Search Results (14)

In the present work, hybrid Cellulose Nanocrystal–MXene (CNC–MXene) nanolubricants were prepared via a two-step method and investigated as potential heat-transfer hybrid nanofluids for the first time. CNC–MXene nanolubricants were synthesized via a two-step method by varying the weight percentage of CNC–MXene nanoparticles (ranging from 0.01 to 0.05 wt%) and characterized using Fourier-Transform Infrared Spectroscopy and TGA (Thermogravimetric Analysis). Response surface methodology (RSM) was used in conjunction with the miscellaneous design model to identify prediction models for the thermophysical properties of the hybrid CNC–MXene nanolubricant. Minitab 18 statistical analysis software and Response Surface Methodology (RSM) based on Central Composite Design (CCD) were utilized to generate an empirical mathematical model investigating the effect of concentration and temperature. The analysis of variance (ANOVA) results indicated significant contributions from the type of nanolubricant (p < 0.001) and the quadratic effect of temperature (p < 0.001), highlighting non-linear interactions that affect viscosity and thermal conductivity. The findings showed that the predicted values closely matched the experimental results, with a percentage of absolute error below 9%, confirming the reliability of the optimization models. Additionally, the models could predict more than 85% of the nanolubricant output variations, indicating high model accuracy. The optimization analysis identified optimal conditions for maximizing both dynamic viscosity and thermal conductivity. The predicted optimal values (17.0685 for dynamic viscosity and 0.3317 for thermal conductivity) were achieved at 30 °C and a 0.01% concentration, with a composite desirability of 1. The findings of the percentage of absolute error (POAE) reveal that the model can precisely predict the optimum experimental parameters. This study contributes to the growing field of advanced nanolubricants by providing insights into the synergistic effects of CNC and MXene in enhancing thermophysical properties. The developed models and optimization techniques offer valuable tools for tailoring nanolubricant formulations to specific tribological applications, potentially leading to improved efficiency and durability in various industrial settings. Full article

This study investigates the potential of a hybrid nanofluid composed of MoS₂ and ZnO nanoparticles dispersed in engine oil, aiming to enhance the properties of a lubricant’s chemical reaction with the Soret effect on a stretching sheet under the influence of an applied magnetic field. With the growing demand for efficient lubrication systems in various industrial applications, including automotive engines, the development of novel nanofluid-based lubricants presents a promising avenue for improving engine performance and longevity. However, the synergistic effects of hybrid nanoparticles in engine oil remain relatively unexplored. The present research addresses this gap by examining the thermal conductivity, viscosity, and wear resistance of the hybrid nanofluid, shedding light on its potential as an advanced lubrication solution. Overall, the objectives of studying the hybrid nanolubricant MoS₂ + ZnO with engine oil aim to advance the development of more efficient and durable lubrication solutions for automotive engines, contributing to improved reliability, fuel efficiency, and environmental sustainability. In the present study, the heat and mass transformation of a Casson hybrid nanofluid (MoS₂ + ZnO) based on engine oil over a stretched wall with chemical reaction and thermo-diffusion effect is analyzed. The governing nonlinear partial differential equations are simplified as ordinary differential equations (ODEs) by utilizing the relevant similarity variables. The MATLAB Bvp4c technique is used to solve the obtained linear ODE equations. The results are presented through graphs and tables for various parameters, namely, M, Q, β, Pr, Ec, Sc, Sr, Kp, Kr, and ${\varphi }_2*$ (hybrid nanolubricant parameters) and various state variables. A comparative survey of all the graphs is presented for the nanofluid (MoS₂/engine oil) and the hybrid nanofluid (MoS₂ + ZnO/engine oil). The results reveal that the velocity profile diminished against the values of M, Kp, and β, and the temperature profile rises with Ec and Q, whereas Pr decreases. The concentration profile is incremented (decremented) with the value of Sr (Sc and Kr). A comparison of the nanofluid and hybrid nanofluid suggests that the velocity f′ (η) becomes slower with the augmentation of ${\varphi }_2*$ whereas the temperature increases when ${\varphi }_2*$ = 0.6 become slower. Full article

This research shows the antifriction and antiwear synergies between a phosphonium ionic liquid (IL) and f-WS₂ and f-SiO₂ nanoparticles (NPs) as additives of a base oil with low viscosity (PAO6). Mass concentrations of 0.1 wt% nanoadditives and 1% IL were selected to formulate the nanolubricants. Pure sliding and rolling–sliding friction tests were performed at 120 °C, finding great friction reductions in comparison with the PAO6 base oil, specifically for the double hybrid nanolubricant (PAO6 + 1 wt% IL + 0.1 wt% f-WS₂ + 0.1 wt% f-SiO₂). Regarding the wear produced, the greatest antiwear behavior was also achieved for the double hybrid nanolubricant (width reduction of 48% and worn area decrease of 84%). Furthermore, by means of Raman microscopy and roughness examination of the worn surfaces, it can be proposed that the lubrication mechanism of doubled hybrid nanolubricants could be supported by the adsorbed tribofilm (IL and f-WS₂) as well as the mending effects (f-WS₂ and f-SiO₂). Full article

In sustainable tribology, researchers are investigating methods to enhance tribological performance by incorporating nanoparticles into lubricants. However, one potential drawback of this strategy is increased lubricant viscosity. The current study aimed to assess the impact of these nanoparticles on the viscosity and coefficient of friction (COF) of the nanolubricants. Three different nanolubricants were synthesized through a two-step process, including mono-nanolubricants (Al₂O₃/DEC PAG and SiO₂/DEC PAG) and hybrid nanolubricants (Al₂O₃-SiO₂/DEC PAG), at volume concentrations between 0.01% and 0.05%. The viscosity and shear flow behavior of these nanolubricants were evaluated using a digital rheometer, while the COF was measured using a Koehler four-ball tribometer. All the nanolubricants showed Newtonian behavior during the experiments. The dynamic viscosity velocity increment of SiO₂/DEC PAG was found to be the lowest (1.88%), followed by Al₂O₃-SiO₂/DEC PAG (2.74%) and Al₂O₃/DEC PAG (3.56%). The viscosity indices of all the nanolubricants were improved only at higher concentrations. At a volume concentration of 0.03%, the Al₂O₃-SiO₂/DEC PAG nanolubricant reduced the COF by up to 8.1%. The results showed that the combination of nanoparticles, temperature, and volume concentration significantly influenced the viscosity and COF of nanolubricants. This study provides essential information for developing high-performance nanolubricants with improved viscosity and COF and advancing environmentally friendly tribology solutions. Full article

Lubricants are essential to machinery life, as they play a crucial role in controlling and diminishing the friction and wear between moving parts when operated under extreme conditions. To this end, due to tight environmental conditions, manufacturers are looking for alternative solid lubricants to be dispersed in base liquid lubricants. MoS₂ and graphene are solid lubricants that provide low frictional properties and high thermal stability in both oxidizing and non-oxidizing environments. This research offers a new lubricant with improved thermal conductivity that combines the synergistic effect of graphene and MoS₂ in a blend of vegetable oil (peanut) and naphthenic oil. The ratio of peanut oil and naphthenic oil varies from 1:3–3:1. A fixed composition of 4.34 wt.% palm oil methyl ester (POME) is added to enhance the anti-wear property further. Graphene and MoS₂ concentrations varied between 1:2–5:2, respectively. This nanoparticle additive oil blend is physically mixed using a water bath sonication for 4 h. The stability of the blend lubricant dispersed with MoS₂ and graphene is studied using a UV-Vis spectrophotometer for 25 days. The effect of various concentrations of graphene, MoS₂, peanut oil, and naphthenic oil on the thermal conductivity of the nanolubricant is also studied as a function of temperature (25 °C–55 °C). Artificial neural network models were used for the parametric investigation of the nanolubricant. It is found that the stability of the formulated nanolubricant increased with peanut oil composition above 25 wt.%. The results show that the 3:1 blend ratio showed higher stability for hybrid MoS₂-based lubricants. Similarly, the highest thermal conductivity is observed for 100 wt.% naphthenic oil with a 1:2 ratio of graphene–MoS₂ at 55 °C. Full article

Poor characterisation of nanoparticle suspensions impedes the development of nanolubricants for use in refrigeration and air-conditioning systems. Chemical treatment techniques, such as surfactants, are inappropriate for enhancing the stability of nanolubricants intended for use in vapour-compression refrigeration (VCR) systems. Prior to incorporating nanolubricants into the system, the stability of TiO₂ and SiO₂ nanoparticles dispersed in PVE was therefore investigated. The nanolubricants were prepared by a two-step method with the aid of an ultrasonication bath homogeniser. Visual observation and ultraviolet–visible (UV–Vis) spectrophotometric analysis were used, and zeta potential analysis was then performed to confirm the nanolubricants’ stability condition. The TiO₂/PVE nanolubricant was observed to be maintained at a 95% concentration ratio for up to 30 days of evaluation. The TiO₂/PVE, SiO_2/PVE, and SiO₂-TiO₂/PVE exhibited zeta potential values of 203.1 mV, 224.2 mV, and 105.3 mV, respectively, after 7 h of sonication. A high absolute value of zeta potential indicates that the electrostatic repulsive forces between nanoparticles are exceptionally strong, indicating an excellent stable suspension. The high values of zeta potentials validated the excellent stability conditions determined by UV–Vis analysis and visual observation. It can be concluded that ultrasonication times of 7 h produced the most stable state for mono- and hybrid nanolubricants. Full article

The tribology properties of TiO₂/POE, SiO₂/POE and TiO₂-SiO₂/POE nanolubricants were investigated for an automotive air-conditioning system with an electrically-driven compressor (EDC). A two-step preparation method was used in dispersing TiO₂ and SiO₂ nanoparticles into Polyol-ester (POE)-based lubricant at different volume concentrations of 0.01 to 0.1%. The coefficient of friction (COF) and wear scar diameter (WSD) were investigated using a Koehler four-ball tribo tester and microscopes. For the TiO₂/POE, SiO₂/POE and TiO₂-SiO₂/POE nanolubricants, respectively, the lowest COFs with maximum reduction were attained at 37.5%, 33.5% and 31.6% each at volume concentrations of 0.05%, 0.01% and 0.03%. The highest WSD reduction for the TiO₂/POE and SiO₂/POE mono nanolubricants were attained at 12.5% and 26.4%, respectively, at the same volume concentration of 0.01%. Meanwhile, the maximum reduction of WSD for the TiO₂-SiO₂/POE hybrid nanolubricant was reached at 12.4% at 0.03% volume concentration. As a conclusion, mono and hybrid nanolubricants with volume concentrations of less than 0.05% are suggested for use in air-conditioning systems with EDC because of their outstanding tribology performances. Further performance investigation of nanolubricants in the air-conditioning system is required to extend the present work. Full article

Stable nanolubricant mixtures are interrelated with thermal conductivity enhancement, thus improving heat transfer performance in automotive air conditioning (AAC) systems. This paper studies the stability and thermal conductivity of double-end capped polyalkylene glycol (PAG)-based nanolubricants specially designed for R1234yf refrigerant. Mono nanolubricants (Al₂O₃/PAG and SiO₂/PAG) and hybrid nanolubricants (Al₂O₃–SiO₂/PAG) were prepared using a two-step preparation method at different volume concentrations of 0.01 to 0.05%. The stability of these nanolubricants was observed by visual, UV-Vis spectrophotometer, and zeta potential. Thermal conductivity (k) was measured from 30 to 70 °C using a C-Therm thermal properties analyser. The results from the stability analysis show that all nanolubricants were confirmed in excellent stability conditions for more than six months with minimum visual sedimentation, more than 70% concentration ratio, and zeta potentials greater than 60 mV. The Al₂O₃–SiO₂/PAG samples recorded the highest values of thermal conductivity increment, followed by the Al₂O₃/PAG and SiO₂/PAG samples with 2.0%, 1.7%, and 1.5% enhancement. Hybrid nanolubricants have been shown to have greater potential in the AAC system because of their excellent stability and better property enhancement in thermal conductivity. Full article

Efficient and effective lubricants have great application prospects in the manufacturing industries. Minimum quantity lubrication (MQL) machining with low flow rate of nanolubricants is investigated for cooling and lubrication during the process. This paper investigates the characterization of graphene-mixed aluminium oxide (G-Al₂O₃) hybrid nanomixture spent lubricants for MQL machining purposes. The main advantage of this method is to reduce the disposal lubricants to develop high-performance cooling-lubrication by using nanolubricants of G-Al₂O₃ nanoparticles in different volume composition ratios at a constant 1.0% volume concentration in a base liquid mixture of 40% spent lubricants. Before conducting the measurements of the nanolubricants’ thermal conductivity and dynamic viscosity, the nanolubricants were homogenous and stable. The tribological performance of all ratios was evaluated by using a four-ball wear tribotester machine. The thermal conductivity peak value for the G-Al₂O₃ hybrid nanolubricant was obtained and the highest enhancement, up to 29% higher than the base liquid solution, was obtained. The dynamic viscosity variation for all ratios was lower than the 40:60 ratio. The properties enhancement ratio suggests that G-Al₂O₃ hybrid nanolubricants with 1.0% volume concentration aid in the heat transfer, especially for ratios of 60:40 and 20:80. The lowest coefficient of friction (COF) for a ratio of 60:40 was obtained to be 0.064, with 45% enhancement as compared to the base liquid solution. In conclusion, optimum ratios for G-Al₂O₃ hybrid nanolubricants were determined to be 20:80 and 60:40. Regarding the properties enhancement ratio, the combination of enhanced thermophysical and tribological properties had more advantages for cooling lubrication application. Full article

To reduce fuel consumption, the automotive air-conditioning (AAC) system’s coefficient of performance (COP) needs to be improved. The use of a diverse selection of hybrid nanolubricant composition ratios is expected to improve the properties of single nanolubricants, resulting in improved AAC system performance. The goal of this study was to find the best combination of hybrid nanolubricants for the best performance of the AAC system. Al₂O₃-SiO₂/PAG hybrid nanolubricants at 0.06% volume concentrations with various composition ratios (20:80, 40:60, 50:50, 60:40, and 80:20) were investigated. An initial refrigerant charge of up to 155 g and a compressor speed of up to 2100 rpm were used in the experiment. The cooling capacity, compressor work, and COP of the AAC system were measured to determine its efficiency. The COP enhancement and compressor work reduction were recorded up to 16.31% and 18.65% for the 60:40 composition ratio, respectively. The maximum cooling capacity up to 75.84% was recorded for the 80:20 ratio, followed by 60:40. The maximum COP value of 8.81 for 155 g of hybrid nanolubricants was obtained at 900 rpm with a 60:40 composition ratio. Therefore, for optimal performance in the AAC system, a 60:40 composition ratio of the Al₂O₃-SiO₂/PAG nanolubricant combination is strongly recommended. Full article

A variety of operational parameters can influence the operation of an automobile air-conditioning (AAC) system. This issue is solved by using optimization techniques that can recommend the ideal parameters for the best results. To improve the performance of AAC system usings Al₂O₃-SiO₂/PAG composite nanolubricants, the response surface method (RSM) was employed. RSM was used to design the experimental work, which was based on a face composite design (FCD). The RSM quadratic models were helpful in determining the links between the input parameters and the responses. The addition of composite nanolubricants improved the overall performance of AAC systems. The parameters were optimized using the RSM’s desirability approach, with the goal of increasing cooling capacity and the coefficient of performance (COP), while reducing compressor work and power consumption. The ideal parameters for the AAC system were found to be 900 rpm compressor speed, 155 g refrigerant charge, and 0.019% volume concentration, with a high desirability of 81.60%. Test runs based on the optimum circumstances level were used to estimate and validate cooling capacity, compressor work, COP, and power consumption. Both predicted and measured values were in good agreement with each other. A new RSM model was successfully developed to predict the optimal conditions for AAC system performance. Full article

Aqueous nanolubricants containing ZrO₂ nanoparticles, graphene oxide (GO) nanosheets, or hybrid nanoparticles of ZrO₂ and GO were formulated using a cost-effective ultrasonication de-agglomeration method. The friction and wear characteristics of these water-based nanolubricants were systematically investigated using a block-on-ring testing configuration with a stainless- and alloy steel contact pair. The concentrations and mass ratios of nanoadditives were varied from 0.02 to 0.10 wt.% and 1:5 to 5:1, respectively, to obtain optimal lubrication performance. The application of a 0.06 wt.% 1:1 ZrO₂/GO hybrid nanolubricant resulted in a 57% reduction in COF and a 77% decrease in wear volume compared to water. The optimised ZrO₂/GO hybrid nanolubricant was found to perform better than pure ZrO₂ and GO nanolubricant in terms of tribological performance due to its synergistic lubrication effect, which showed up to 54% and 41% reductions in friction as well as 42% and 20% decreases in wear compared with 0.06 wt.% ZrO₂ and 0.06 wt.% GO nanolubricants. The analysis of wear scars revealed that using such a ZrO₂/GO hybrid nanolubricant yielded a smooth worn surface, with 87%, 45%, and 33% reductions in S_a compared to water and 0.06 wt.% ZrO₂ and 0.06 wt.% GO nanolubricants. The superior tribological performance can be ascribed to the combination of the rolling effect of ZrO₂ nanoparticles and the slipping effect of GO nanosheets. Full article

In this paper, the thermal conductivity behavior of synthetic and natural esters reinforced with 2D nanostructures—single hexagonal boron nitride (h-BN), single molybdenum disulfide (MoS₂), and hybrid h-BN/MOS₂—were studied and compared to each other. As a basis for the synthesis of nanofluids, three biodegradable insulating lubricants were used: FR3^TM and VG-100 were used as natural esters and MIDEL 7131 as a synthetic ester. Two-dimensional nanosheets of h-BN, MoS_2, and their hybrid nanofillers (50/50 ratio percent) were incorporated into matrix lubricants without surfactants or additives. Nanofluids were prepared at 0.01, 0.05, 0.10, 0.15, and 0.25 weight percent of filler fraction. The experimental results revealed improvements in thermal conductivity in the range of 20–32% at 323 K with the addition of 2D nanostructures, and a synergistic behavior was observed for the hybrid h-BN/MoS₂ nanostructures. Full article

The tribological performances of the SiO₂/MoS₂ hybrids as lubricant additives were explored by a reciprocating ball-on-flat tribometer for AZ31 magnesium alloy/AISI 52100 bearing steel pairs. The results demonstrated that the introduction of SiO₂/MoS₂ hybrids into the base oil exhibited a significant reduction in the friction coefficient and wear volume as well as an increase in load bearing capacity, which was better than the testing results of the SiO₂ or MoS₂ nanolubricants. Specifically, the addition of 0.1 wt % nano-SiO₂ mixed with 1.0 wt % nano-MoS₂ into the base oil reduced the friction coefficient by 21.8% and the wear volume by 8.6% compared to the 1.0 wt % MoS₂ nanolubricants. The excellent lubrication behaviors of the SiO₂/MoS₂ hybrid nanolubricants can be explained by the micro-cooperation of different nanoparticles with disparate morphology and lubrication mechanisms. Full article