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Fuel lubricity is an essential property that ensures the longevity end efficiency of diesel CI engines. Nanomaterials have been shown to have the potential to improve lubricity in many different lubricating substances, including fuels. Moreover, the combustion process has also been shown to improve with the introduction of nanomaterials. This study investigated a series of nanoparticles, including carbon nanoplates, carbon nanotubes, aluminum oxide, zinc oxide, and cerium oxide, as lubricity-enhancing additives for selected fuels. Conventional diesel fuel and rapeseed oil methyl ester, referred to as biodiesel, were chosen as base fuels for modification. The lubricity was evaluated according to the standard test method ASTM 6079 using the HFRR tribometer. The leading lubricity indicators were the wear scar diameter, wear volume, and coefficient of friction. In addition, the worn surface analysis was performed to elucidate the lubrication mechanism. The results show that the addition of nanoparticles can improve the lubricity of both investigated fuels. However, the effect differed among nanoparticles and fuels. In summary, carbon nanotubes could be a rational choice for both fuels. In addition, zinc oxide improved the lubricity of diesel fuel, while carbon nanoplatelets and aluminum oxide nanoparticles showed improvements in the lubricity of biodiesel.

The rheological, ignition, and tribological properties of lubricating oils diluted with biodiesel were analyzed. The flash point tFP, calculated cetane index CCI, density ρ, coefficient of the temperature density change ε, kinematic viscosity ν, dynamic viscosity η, viscosity index VI, and lubricity during a High-Frequency Reciprocating Rig (HFFR) test (x, y, WSD, and WS1.4) and lubricating conditions during an HFFR test (oil film resistance FILM and friction coefficient μ) were determined. The test was performed for the oil mixtures of the lubricating oil of the SAE 30 and SAE 40 viscosity grades, which were diluted with the biodiesel blend (D93B7—diesel oil with 7% v/v fatty acid methyl esters, FAME) at concentrations of diesel oil in the mixture equal to 0% (pure lubricating oil), 1%, 2%, 5%, 10%, 20%, 30%, 50%, and 75% m/m, respectively. The experiment confirmed the existence of clear relationships between the increase in the dilution of lubricating oil with tested biodiesel blend and tFP, ρ, ε, ν, η, and VI, and the deterioration of lubrication conditions. It is recommended to take remedial action even in the case of low diesel oil concentration (

During coal-based power generation, fuel oil is used to assist with ignition of pulverised coal. Fuel oil passes through several pieces of equipment on its way to the burner section of the boiler. In this article the focus is on the lubricity behaviour of three representative fuel oil types and on the potential blocking of filters and nozzles caused by the presence of unwanted components in these fuel oils. The high frequency reciprocating rig (HFRR) (ISO 12156-1) was used to determine the lubricity of these fuel oils at different temperatures. Results indicate that the presence of asphaltenes (components of heavy fuel oils with complex aromatic structures) changes the viscosities of fuel oils, which, in turn affect their lubricity behaviour. Medium wax-blend fuel oil (MFO) containing high molecular weight paraffins (wax), low concentrations of asphaltenes and solid particles caused less friction and wear (with coefficient of friction (COF) values below 0.1) and good high temperature performance. Crude-derived heavy fuel oil (HFO), containing high concentrations of asphaltenes and solid particles caused very high coefficients of friction (COF peaks above 0.3) and severe abrasive wear at high temperatures. Although the third fuel oil tested was a light cycle oil (LFO) and did not contain any asphaltenes, results indicated a sensitivity to oxidation, increasing with temperature, which can have an adverse effect on in situ performance.

Graphene has shown great potential in the lubrication field due to its excellent mechanical property and interlayer self-lubricating peculiarity. However, graphene is difficult to directly apply as intrinsic lubricants and its chemical inertness also restricts the further improvement of lubrication performances. Inspired by the advanced lubrication system of natural snail mucus, a solvent-free graphene-based nanofluid with three-dimensional and multiple adsorption networks was fabricated by functionalization of fluorinated graphene with highly chemical activity of C–F bonds and high functionalization density (F/C ≈ 1.0). The dendritic polyethyleneimine (PEI) and the polyacrylic acid (PAA) were grafted onto the surface of graphene in turn, which endows nanofluids with a good fluidity under room temperature. Moreover, the introduced PEI and PAA synergistically contribute the three-dimensional and multiple adsorption effects like coordination and charge interactions (Fe–N and Fe3+-COO-) on the surface of friction pairs, which enables to form the stable and tough tribofilms. Therefore, it presents a good intrinsic lubricity with a low friction coefficient of ∼0.15 without obvious run-in time. Meanwhile, because of the excellent hydrophilicity, adding even small fraction of nanofluids into water reduces vastly the friction coefficient and wear rate with about 60% and 59%, respectively.

Summary Although advances in coating technologies have allowed us to match—or even exceed—the lubricity of Nature’s low-friction surfaces, the performance of synthetic materials inevitably diminishes over time as the surfaces are worn and damaged by irreversible breakage of covalent bonds. Synthetic systems lack the bespoke repair mechanisms that replenish hydration lubrication surfaces in Nature. Here, we demonstrate dynamic repair of low-friction surfaces prepared through a surface-selective self-assembly strategy. Monolayers of lubricating polymers associate with functionalized surfaces through strong and specific host–guest interactions, leading to hydration lubrication surfaces with low coefficients of friction (0.024–0.028). Following friction-induced dissociation of the polymers, the polymer-to-surface interaction is restored by the reformation of host–guest complexes, thus repairing the monolayer, renewing the lubricity, and reducing the effects of wear. Such dynamically restored low-friction materials will be an essential tool in decreasing global energy use—a fifth of which is expended overcoming friction.

Hypothesis A catanionic surface-active ionic liquid (SAIL) trihexyltetradecylphosphonium 1,4-bis(2-ethylhexoxy)-1,4-dioxobutane-2-sulfonate ([P6,6,6,14] [AOT]) is nanostructured in the bulk and at the interface. The interfacial nanostructure and lubricity may be changed by applying a potential. Experiments The bulk structure and viscosity have been investigated using small angle X-ray scattering (SAXS) and rheometry. The interfacial structure and lubricity as a function of potential have been investigated using atomic force microscopy (AFM). The electrochemistry has been investigated using cyclic voltammetry. Findings [P6,6,6,14] [AOT] shows sponge-like bulk nanostructure with distinct interdigitation of cation–anion alkyl chains. Shear-thinning occurs at 293 K and below, but becomes less obvious on heating up to 313 K. Voltammetric analysis reveals that the electrochemical window of [P6,6,6,14] [AOT] on a gold micro disk electrode exceeds the potential range of the AFM experiments and that negligible redox activity occurs in this range. The interfacial layered structure of [P6,6,6,14] [AOT] is weaker than conventional ILs and SAILs, whereas lubricity is better, confirming the inverse correlation between the near-surface structure and lubricity. The adhesive forces of [P6,6,6,14] [AOT] are lower at −1.0 V than at open circuit potential and +1.0 V, likely due to reduced electrostatic interactions caused by shielding of charge centres via long alkyl chains.

This paper reported the tribological behavior of 20 nm size TiO2 nanoparticles added in mineral-based SN-500 oil. All experimental tests were conducted on lubricating oils under different loads and concentrations of nanoparticles. Wear and friction analysis have been done by using pin on disc tribometer. As per results, TiO2 nanoparticles drastically improved tribological properties such as wear, friction and lubricity of oil at 0.5 wt% and 0.75 wt% concentrations of nanoparticles. Also a TiO2 nanoparticle improves load carrying ability of base oil because spheroidal geometry of TiO2 nanoparticles plays ball bearing effect between two mating surfaces. Due to 20 nm sized TiO2 nanoparticles fill debris on metal surfaces, So that friction will be automatically minimized. In addition, rough surface wear analysis analyzed using a scanning electron microscope (SEM).

Various detrimental effects of petroleum-based lubricants have encouraged the use of vegetable oil as a replacement due to its better lubricity and environmental friendliness. This study evaluated the performance of virgin and emulsified vegetable oil as cutting fluid for the turning of titanium alloy with ceramic inserts. The performance was determined using signal to noise (S/N) ratio with few input parameters such as lubricant type, cutting speed, feed rate, and depth of cut. Palm oil and coconut oil were used as the vegetable oil. The virgin oil was mixed with a portion of water to produce emulsified oil. The machining operation applied minimum quantity lubrication (MQL) throughout the experiment. The performance of each type of oil was evaluated in terms of S/N ratio for cutting temperature, and chip reduction coefficient, and percentage of cutting tool wear in order to obtain the best cutting condition. Results showed that the virgin palm oil had better performance on the cutting temperature, tool wear, and chip reduction coefficient. Furthermore, the virgin coconut produced better performance compared to emulsified coconut oil. Hence, it is concluded that virgin vegetable oils perform better as cutting fluid compared to emulsified vegetable oil.

Healthy articular cartilage supports load bearing and frictional properties unmatched among biological tissues and man-made bearing materials. Balancing fluid exudation and recovery under loaded and articulated conditions is essential to the tissue's biological and mechanical longevity. Our prior tribological investigations, which leveraged the convergent stationary contact area (cSCA) configuration, revealed that sliding alone can modulate cartilage interstitial fluid pressurization and the recovery and maintenance of lubrication under load through a mechanism termed ‘tribological rehydration.’ Our recent comparative assessment of tribological rehydration revealed remarkably consistent sliding speed-dependent fluid recovery and lubrication behaviors across femoral condyle cartilage from five mammalian species (equine/horse, bovine/cow, porcine/pig, ovine/sheep, and caprine/goat). In the present study, we identified and characterized key predictive relationships among tissue properties, sliding-induced tribological rehydration, and the modulation/recovery of lubrication within healthy articular cartilage. Using correlational analysis, we linked observed speed-dependent tribological rehydration behaviors to cartilage's geometry and biphasic properties (tensile and compressive moduli, and permeability). Together, these findings demonstrate that easily measurable biphasic tissue characteristics (e.g., bulk tissue material properties, compressive strain magnitude, and strain rates) can be used to predict cartilage's rehydration and lubricating abilities, and ultimately its function in vivo. Statement of significance In healthy cartilage, articulation recovers fluid lost to static loading thereby sustaining tissue lubricity. Osteoarthritis causes changes to cartilage composition, stiffness, and permeability associated with faster fluid exudation and presumably poorer frictional outcomes. Yet, the relationship between mechanical properties and fluid recovery during articulation/sliding remains unclear. Through innovative, high-speed benchtop sliding and indentation experiments, we found that cartilage's tissue properties regulate its exudation/hydration under slow sliding speeds but have minimal effect at high sliding speeds. In fact, cartilage rehydration appears insensitive to permeability and stiffness under high fluid load support conditions. This new understanding of the balance of cartilage exudation and rehydration during activity, based upon comparative tribology studies, may improve prevention and rehabilitation strategies for joint injuries and osteoarthritis.

In an attempt to avoid serious problems that can affect the efficiency of refueling ground-operated vehicles and aircraft during military operations, the Armed Forces of the North Atlantic Treaty Organization (NATO) are introducing the use of a unique fuel for both air and land use. The fuel that has been selected is the F-34, similar to Jet A-1, which is used in civil aviation, in order to replace diesel fuel in many applications. It has to be mentioned that tests performed with this fuel, which is kerosene type on the high frequency reciprocating rig (HFRR) have shown that such fuel is responsible for severe wear. This very high wear is related to the very low lubricity of aviation fuel. Having the idea to improve the lubricity of aviation fuel to the level of fuels used in compression ignition engines (diesel fuel), seven N,N-Bis(2-ethoxyethyl) fatty acid amides were formulated from various vegetable oils (sunflower oil, soybean oil, cottonseed oil, olive oil, tobacco seed oil, coconut oil, used frying oil), and they were evaluated as lubricity improvers of the aviation fuel. The required tribological measurements for lubricity rating were carried out by employing ISO 12156-1 test method on an HFRR instrument. The test conditions during the measurements were in the range of 55% to 58% for the relative humidity and 24 °C for the temperature. The results from the tribological measurements showed that all N,N-Bis(2-ethoxyethyl) fatty acid amides used were rated as efficient in order to provide an acceptable mean wear scar diameter (below 460 μm) at concentrations from 150 to 300 ppm. Additive concentrations below 150 ppm did not improve the lubricity at the required level. The increase of N,N-Bis(2-ethoxyethyl) fatty acid amides at concentrations over 300 ppm did not have any significant decrease in the wear scar diameter. A comparison between the N,N-Bis(2-ethoxyethyl) fatty acid amides showed that those formulated by non-polyunsaturated oils like olive oil and coconut oil seem to have better lubricity improver characteristics.

Fuel contamination of engine lubricating oil has been previously determined to arise from two independent phenomena: the effect on oil flash point, and the effect of changing lubrication conditions on tribological pairs. This paper combines these effects and holistically analyzes the consequences of fuel in the lubricating oil of a trunk piston engine on the risk of crankcase explosion. The author hypothesized that diesel fuel as an oil contaminant increases the risk of an explosion in the crankcase of an engine due to the independent interaction of two factors: (1) changes in the oil’s combustible properties, and (2) deterioration of the lubrication conditions of the engine’s tribological nodes, such as main bearings, piston pins, or crank bearings. An experiment was performed to evaluate the rheological, ignition, and lubrication properties of two oils (SAE 30 and SAE 40) commonly used for the recirculation lubrication of marine trunk piston engines for different levels of diesel contamination. The hypothesis was partially confirmed, and the results show that contamination of the lubricating oil with diesel fuel in an amount of no more than 10% does not significantly affect the risk of explosion in the crankcase. However, diesel concentrations above 10% call for corrective action because the viscosity index, lubricity, coefficient of friction and oil film resistance change significantly. Deterioration of the tribological conditions of the engine bearings, as seen in the change in viscosity, viscosity index, and lubricity of the oil, causes an increase in bearing temperature and the possibility of hot spots leading to crankcase explosion.

Over the past decade, regulations have been changed to reduce the environmental impact of diesel fuel reducing the content of sulphur and aromatics. This has resulted in a deterioration of low-temperature properties and lubricity. Also more attention has been given to renewability of the products to lessen the impact on the environment. To overcome this problem we synthesized biolubricants that improve lubricity but do not deteriorate low-temperature properties. Through the esterification and transesterification reaction, we synthesized esters from levulinic acid and waste sunflower oil, and alcohols with different shapes and chain lengths, to investigate the influence of the source of the raw material and the selected alcohol on the application properties of the fuel formulations. To test the influence of bioadditives on the properties of diesel fuel, formulations of diesel and bioadditives with a concentration of up to 10 wt% (from levulinic acid) and up to 20 vol% (from linoleic and oleic acid derived from waste sunflower oil) were prepared. The formulations were tested for density, kinematic viscosity, pour point, and lubricity. From the results obtained, the bioadditives affect slightly the density and viscosity, but all values still remain within the standard limits meaning they won’t affect the quality of combustion. The synthesized bioadditives had no negative effect on the pour point, while the lubricity of the diesel formulations improved by more than 40%.

The electrostatic assembly and spark plasma sintering (SPS) technology were used to prepare reduced graphene oxide‑carbon nanotube/copper (rGO-CNTs/Cu) composites. In this process, graphene oxide and carbon nanotubes (CNTs) are first used to construct a three-dimensional network structure of rGO-CNTs hybrid reinforcement in a copper matrix, which synergistically enhance the performance of copper matrix composites. The results show that the hardness of rGO0.9-CNTs0.1/Cu composites is up to 105.2 HV, and the electrochemical corrosion rate is reduced by 38.9% compared with that of rGO/Cu composites. In addition, with CNTs adding, rGO-CNTs formed a lubricating film, which hindered the friction surface contact between the grinding material and the composites. The lowest friction coefficient of rGO0.5-CNTs0.5/Cu composites is only 0.387. It reduces the coefficient of friction and improves the lubricity of the friction surface of rGO-CNTs/ composites

Regulating rheological properties of water-based drilling fluids has always been a hot topic. This paper proposed a new method for regulating rheological properties of water-based drilling fluids by ultrasonic field. The experimental results showed that the ultrasound increased the viscosity and yield point of bentonite suspension by reducing the particle size of clay, destroying the network structure between clay particles, increasing the mud yield and the cation exchange capacity of bentonite, and promoting the hydration dispersion of bentonite. The change of rheological property showed a memory effect at room temperature and high temperature. Besides, the ultrasonic energy affected the network structure between clays and polymer chains, thus regulating the rheological properties of the bentonite-polymer system. For two types of drilling fluids investigated, the rheology of the poly-sulfonate drilling fluid was regulated by damaging the grid structure between additives and clays by low-power ultrasound and reducing the clay particle size by high-power ultrasound, while the rheology of the deep-water drilling fluid was mainly regulated by disentangling the spatial grid structure between additives. Additionally, ultrasound showed no effect on the lubricity, inhibition and stability of drilling fluids, which proved the feasibility of ultrasound to regulate rheological properties of water-based drilling fluids.

This study focused on evaluating the lubricity of diesel–biodiesel fuel with oxygenated alcoholic and nano-particle additives. Fuel injection system lubrication depended primarily on the fuel used in the diesel engine. Palm–sesame oil blend was used to produce biodiesel using the ultrasound-assisted technique. B30 fuel sample as a base fuel was blended with fuel additives in different proportions prior to tribological behavior analysis. The lubricity of fuel samples measured using HFRR in accordance with the standard method ASTM D6079. All tested fuels’ Tribological behavior examined through worn steel balls and plates using scanning electron microscopy (SEM) to assess wear scar diameter and surface morphology. During the test run, the friction coefficient was measured directly by the HFRR tribometer system. The results exhibited that B10 (diesel) had a very poor coefficient of friction and wear scar diameter, among other tested fuels. The addition of oxygenated alcohol (ethanol) as a fuel additive in the B30 fuel sample decreased the lubricity of fuel and increased the wear and friction coefficient, among other fuel additives. B30 with DMC showed the least wear scar diameter among all tested fuels. B30 with nanoparticle TiO 2 exhibited the best results with the least wear scar diameter and lowest friction coefficient among all other fuel samples. B30+DMC demonstrated significant improvement in engine performance (BTE) and carbon emissions compared to different tested samples. B30+TiO2 also showed considerable improvement in engine characteristics.

Intriduction. The environmental safety of cars with a diesel engine does not lose its relevance. In the conditions of stricter requirements for diesel fuel, the content of many substances harmful to the environment, including sulfur, is not allowed. As is known, low-sulfur fuels require the presence of additives that improve the lubricating properties of diesel fuel. Non-compliance with the requirements for lubricity significantly affects the resource of the fuel supply system of a diesel engine, primarily the Common Rail system. In order with the circumstances listed above, we hypothesized that vegetable oil can serve in small concentrations to improve the lubricating properties of fuels.Materials and methods. In our research, we conducted experiments using the standard HFRR method (highfrequency translational motion of a ball rubbing against a plate in fuel). A microscope was used to visually assess the wear spots and measure their size. Diesel fuel was taken as samples for experiments and vegetable oil was added to it as an additive in certain proportions.Discussion and conclusions. The vegetable oil additive can improve the lubricity of diesel fuel, even if it does not comply with GOST for this parameter. The experiments conducted allow us to conclude that the vegetable oil additive as a percentage of diesel fuel almost linearly reduces the diameter of the wear spot

Water-based suspensions with nanoparticles as additives have been developed to replace oil-based lubricants for green manufacturing. Optimisation of nanosuspension formulation can enhance their performance and thereby reduce manufacturing costs. Nevertheless, developing high-performance water-based nanosuspensions requires an in-depth understanding of the role of nanoadditives in lubrication. This review summarises the formulation of water-based nanosuspensions, their tribological properties, and lubrication mechanisms. Technical issues are systematically addressed concerning the applications of nanosuspensions in the rolling of steels, machining of difficult-to-cut metals, and abrasive shaping of hard-brittle ceramics. This review facilitates understanding water-based nanolubrication to enable formulating nanosuspensions with a satisfactory manufacturing performance. The review outcomes indicate that oxide-based nanosuspensions are suitable candidates for metal forming and machining processes due to their excellent anti-wear performance and high heat-carrying capacity. Carbon-based nanosuspensions are appropriate for ceramic shaping processes due to their excellent lubricity and superior resistance against abrasion. In particular, hybrid nanosuspensions consisting of at least two different types of nanoparticles demonstrate a superior synergistic performance in lubrication and cooling. They hence have great potential for future manufacturing processes for both ductile and brittle materials.

Depletion of mineral reservoirs along with health and environmental concerns have led to a greater focus on bio-lubricants. The purpose of this study was to analyze and optimize the reaction conditions of the transesterification process for cotton biolubricant synthesis by using Response Surface Methodology (RSM). In RSM, Rotatable central composite design was selected to examine the effect of reaction input factors on the yield of cotton bio-lubricant during the transesterification process. ANOVA analysis showed that temperature was the most significant factor followed by time, pressure and catalyst-concentration. Optimum reaction conditions obtained by RSM for maximum TMP tri-ester (cotton bio-lubricant) yield of about 37.52% were 144 °C temperature, 10 h time, 25 mbar pressure, and 0.8% catalyst-concentration. RSM predicted results were successfully validated experimentally and by artificial neural networking. About 90%–94% cotton seed oil bio-lubricant was obtained after purification and its physiochemical, lubricity and tribological properties were evaluated and found comparable with ISO VG-46 and SAE-40 mineral lubricant. Hence, cottonseed oil is a potential source for the bio-lubricant industry.

Instrumental characteristics from extensional rheology and tribology for aqueous xanthan gum (XG) and locust bean gum (LBG) solutions were studied in the presence or absence of simulated saliva. Extensional viscosity was calculated from the filament shrinkage behavior using a capillary breakup extensional rheometer, whereas the friction coefficient was measured using a set-up consisting of polydimethylsiloxane substrate and a glass ball bearing on a rotational rheometer. Increase in extensional viscosity was detected immediately after initiation of extensional flow, particularly XG, and also immediately before the filament rupture, particularly LBG. Extensional viscosity tended to decrease with increased addition of simulated saliva for XG, while to increase for LBG. In both cases, effect of cations in the saliva was greater than that of mucin. From the shape of the Stribeck curve (i.e., dependence of the friction coefficient on the entrainment speed) and comparison of the friction coefficient itself, lubricity of XG was greater than that of LBG. Simulated saliva added decreased the friction coefficient for each polysaccharide through functions of cations rather than mucin. Extensional viscosity and tribological measurements revealed mechanical properties of polysaccharide solutions which cannot be determined or quantified by shear viscosity alone.

Sulfide was used as solid lubricant, and MoS2 was popular. It was used industry as powder shape. Sulfur as oil additive; ZDDP, MoTDC were also well known. These composites make tribofilm which prevent seizure, scoring and some tribological troubles. In this paper, sulfides were synthesized by powder metallurgy technics. In addition, these sulfides were mixed with bronze powders and sintered as cylindrical specimen. As a result of the friction test in the lubricated condition, tribofilm were covered with specimen surface. By XPS observation, sulfides and oxides were detected on the specimen surface. In the test, additive was not contained in the lubricant because PAO as base oil was adapted. However, sulfide in the specimen affect the making the tribofilm, especially when bornite (Cu5FeS4) was used.

Friction and high temperatures greatly affect machining efficiency when machining superalloy materials. Nanoparticles with high thermal conductivity and lubricity are preferred for increase lubricant performance. Nanofluids prepared with nanoparticles not only reduce environmental concerns but also positively affect the machining efficiency in the sustainable manufacturing process. However, some nanoparticles added in mono form stand out with their thermal conductivity and some nanoparticles with their lubricating performance. For this reason, the lubrication performance of hybrid nanofluids prepared with nanoparticles with different superior properties is a matter of interest. In this study, the machining performance of Inconel X-750 superalloy was investigated by using hexagonal boron nitride (hBN), graphite (Grpt), and MoS2 nanoparticles with different shapes and properties. For this purpose, the milling experiments were performed under three different hybrid nanofluid (hBN/Grpt, hBN/MoS2, and Grpt/MoS2) conditions, at three different cutting speeds (30, 45, and 60 m/min), and three different feed rates (0.05, 0.10, and 0.15 mm/rev). Cutting force, cutting temperature, surface roughness/topography, tool wear, and tool life were selected as machining performance criteria. According to the results obtained from the experiments, it was understood that the hBN/Grpt hybrid nanofluid outperformed hBN/MoS2 and Grpt/MoS2 conditions in all performance criteria. hBN/Grpt hybrid nanofluid achieved 36.17% and 6.08% improvement in tool life compared to Grpt/MoS2 and hBN/MoS2 nanofluids, respectively. Duzce University (Turkey) Research FundDuzce University [2017.07.04.593] The authors wish to thank the Duzce University (Turkey) Research Fund for their financial support of this experimental study (Project Number: 2017.07.04.593). WOS:000696326900006 2-s2.0-85114105505

In the present study, we demonstrated a novel process of in-situ fabrication of graphene sheets by adopting the chemical vapor deposition (CVD) method. Fabricating such a layer of vertical graphene sheets (VGs) on the surface of microcrystalline diamond (MCD) films could decrease the stable coefficient of friction (COF) by 20–30%. Besides, such lubricity showed excellent load capacity and durability. With normal loads ranging from 3 N to 9 N (Hertz contact pressure of 2.1–3.1 GPa), the MCD-VGs films exhibited COFs stabilized at 0.105 and wear rates less than 5 × 10−6 mm3 N−1 m−1. Additionally, the produced VGs displayed an excellent service lifetime with 72,000 sliding cycles. During the friction tests, an equilibrium graphene self-mated contact formed on the sliding interface as graphene fragments adhered onto the counterpart ball and resulted in the reduction of friction and low wear rates. Additionally, the mixtures of Si3N4/SiO2 particles and graphene sheets residual within the wear tracks would promote the transformation of the sliding regime to three-body abrasion, beneficial for friction reduction. The findings presented in this study provide a novel and effective approach to enhance the lubricity of any engineering diamond surface.

Dilution of engine oil with unburned fuels alters its lubricity and tribological properties. In this research paper, SAE-40 lubricating oil samples were contaminated with known percentages (5%) of fuels (diesel, palm-sesame biodiesel blend (B30), B30 + ethanol, B30 + dimethyl carbonate, B30 + carbon nanotubes and, B30 + titanium oxide). The effect of all these fuels on wear and frictional characteristics of lubricating oil was determined by using a 4-ball tribo tester and wear types on worn surfaces were analyzed by using SEM. Lubricating oil diluted with B10 (commercial diesel) showed highest COF (42.95%) with severe abrasive and adhesive wear than mineral lubricant among other fuels. Lubricating oil diluted with palm-sesame biodiesel (B30 blend) with alcoholic additives showed comparatively less COF, less wear scar diameter and polishing wear due to presence of ester molecules. Lub + B30 + Eth exhibited increment in COF value (35.81%) compared to SAE-40 mineral lubricant. While lubricating oil contaminated with B30 with nanoparticles showed least frictional characteristics with abrasive wear. Lub + B30 + TiO2 showed least increment in COF value (13.78%) among all other contaminated fuels compared to SAE-40 mineral lubricant. It is concluded that nanoparticles in biodiesel blends (B30) helps in reducing degradation of lubricants than alcoholic fuel additives and commercial diesel. (C) 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Alexandria University.

The main purposes of this research were to study the diesel engines' performance and emission characteristics of quaternary fuels, as well as to analyze their tribological properties. The quaternary comprised waste plastic pyrolysis oil, waste cooking oil biodiesel, palm oil biodiesel, and commercial diesel. Their compositions were analyzed by gas chromatography and mass spectrometry. By using mechanical stirring, four quaternary fuels with different compositions were prepared. Because Malaysia is expected to implement B30 (30% palm oil biodiesel content in diesel) in 2025, B30a (30% palm oil biodiesel and 70% commercial diesel) mixture was prepared as a reference fuel. In total, 5%, 10%, and 15% of each waste plastic pyrolysis oil and waste cooking oil biodiesel were mixed with palm oil biodiesel –commercial diesel mixture to improve fuel characteristics, engine performance, and emission parameters. The palm oil biodiesel of the quaternary fuel mixture was kept constant at 10%. The results were compared with B30a fuel and B10 (10% for palm oil biodiesel and 90% for diesel; commercial diesel). The findings indicated that compared with B30a fuel, the brake power and brake thermal efficiency of all quaternary fuel mixtures were increased by up to 2.78% and 9.81%, respectively. Compared with B30a, all quaternary fuels also showed up to a 6.31% reduction in brake-specific fuel consumption. Compared with B30a, the maximum carbon monoxide and carbon dioxide emissions of B40 (60% commercial diesel, 10% palm oil biodiesel, 15% waste plastic pyrolysis oil and 15% waste cooking oil biodiesel) quaternary fuel were reduced by 19.66% and 4.16%, respectively. The B20 (80% commercial diesel, 10% palm oil biodiesel, 5% waste plastic pyrolysis oil and 5% waste cooking oil biodiesel) quaternary blend showed a maximum reduction of 41.86% in hydrocarbon emissions collated to B30a. Compared with B10, the average coefficient of friction of the quaternary fuel mixture of B40, B30b (70% commercial diesel, 10% palm oil biodiesel, 10% waste plastic pyrolysis oil and 10% waste cooking oil biodiesel), and B20 were reduced by 3.01%, 1.20%, and 0.23%, respectively. Therefore, the quaternary blends show excellent utilization potential in diesel engine performance.

Frost accretion occurs ubiquitously in various industrial applications and causes tremendous energy and economic loss, as manifested by the Texas power crisis that impacted millions of people over a vast area in 2021. To date, extensive efforts have been made on frost removal by micro-engineering surfaces with superhydrophobicity or lubricity. On such surfaces, air or oil cushions are introduced to suspend the frost layer and promote the rapid frost sliding off, which, although promising, faces the instability of the cushions under extreme frosting conditions. Most existing hydrophilic surfaces, characterized by large interfacial adhesion, have long been deemed unfavorable for frost shedding. Here, we demonstrated that a hydrophilic and slippery surface can achieve efficient defrosting. On such a surface, the hydrophilicity gave rise to a highly interconnected basal frost layer that boosted the substrate-to-frost heat transfer; then, the resulting melted frost readily slid off the surface due to the superb slipperiness. Notably, on our surface, the retained meltwater coverage after frost sliding off was only 2%. In comparison to two control surfaces, for example, surfaces lacking either hydrophilicity or slipperiness, the defrosting efficiency was 13 and 19 times higher and the energy consumption was 2.3 and 6.2 times lower, respectively. Our study highlights the use of a hydrophilic surface for the pronounced defrosting in a broad range of industrial applications.

Four nonhalogenated ionic liquids (ILs) based on the same phosphonium cation are investigated in terms of the anion suitability for enhancing the lubricity of a biodegradable oil. For all test cond ...

The present work intended to develop an invert emulsion drilling mud from biodegradable neem seed oil as an alternative to conventional diesel-based drilling mud. This would present comparable properties and performances with API standard requirements, ecologically friendly and at a low cost. Biodiesel produced from non-edible neem oil was used as the continuous phase in an invert emulsion-based drilling mud. Different tests to investigate the applicability of the mud for drilling applications were conducted. The rheological and lubricity tests results indicate that the neem oil biodiesel-based drilling muds are comparable with conventional diesel-based drilling muds. The produced biodiesel shows a significantly better flash point of 168 �C than the traditional diesel flash point of 70 �C; indicating better fire safety than the conventional diesel. The lubricity and rheological data indicate the formulated mud with neem seed oil biodiesel fair reasonably well with conventional diesel and within the API requirements. In general, the preliminary results show that neem oil biodiesel is a potential alternative to conventional organic oil in formulating oil-based drilling mud in terms of technical and environmental analysis.

Basil seed, containing anionic heteropolysaccharides in its outer pericarp, swells as gelatinous hydrocolloid when soaked in water. In this study, basil seed powder (BSP) was used as a multifunctional additive for water-based drilling fluids. The chemical composition, water absorbency, rheological properties of aqueous suspension of BSP were tested. The effect of BSP on the rheological and filtration of bentonite-based drilling fluid before and after thermal aging was investigated. The inhibition characteristics were evaluated by linear swelling, shale cuttings dispersion and shale immersion test. Lubricity improvement by BSP was measured with extreme pressure lubricity test. The results revealed that incorporation of BSP into bentonite suspension improved rheological and filtration properties effectively after thermal aging of 120 °C. BSP exhibited superior inhibitive capacity to xanthan and synergistic effect with KCl. BSP could reduce friction by forming hydration layer. The nanoscale three-dimensional network structures enable BSP to maintain high water retention and absorb strongly on bentonite and metal surface, contributing to enhanced rheology, filtration, inhibition and lubrication properties. The versatile characteristic of BSP, as well as biodegradation makes it a promising additive using in high performance water-based drilling fluid and a potential alternative to conventional synthetic polymers.

This research was aimed to examine the diesel engine’s performance and emission of secondary fuels (SFs), comprising waste plastic oil (WPO) and palm oil biodiesel (POB), and to analyze their tribological properties. Their compositions were analyzed by gas chromatography–mass spectrometry (GC–MS). Five SFs (10–50% POB in WPO) were prepared by mechanical stirring. The results were compared to blank WPO (WPO100) and Malaysian commercial diesel (B10). WPO90 showed the maximum brake power (BP) and brake torque (BT) among the SFs, and their values were 0.52 and 0.59% higher compared to B10, respectively. The increase in POB ratio (20–50%) showed a negligible difference in BP and BT. WPO70 showed the lowest brake-specific fuel consumption among the SFs. The brake thermal efficiency (BTE) increased with POB composition. The maximum reductions in emission of hydrocarbon (HC, 37.21%) and carbon monoxide (CO, 27.10%) were achieved by WPO50 among the SFs. WPO90 showed the maximum reduction in CO2 emission (6.78%). Increasing the POB composition reduced the CO emissions and increased the CO2 emissions. All SFs showed a higher coefficient of friction (COF) than WPO100. WPO50 showed the minimal increase in COF of 2.45%. WPO90 showed the maximum reduction in wear scar diameter (WSD), by 10.34%, compared to B10. Among the secondary contaminated samples, SAE40-WPO90 showed the lowest COF, with 5.98% reduction compared to SAE40-WPO100. However, with increasing POB content in the secondary contaminated samples, the COF increased. The same trend was also observed in their WSD. Overall, WPO90 is the optimal SF with excellent potential for diesel engines.

Chemical degradation is a critical matter related to synthetic oil. Putranjiva oil has the potency to be a synthetic oil alternative and is readily accessible in India. During this research, the oil was epoxidized to strengthen the oxidation stability of the Putranjiva oil. In addition, silicon dioxide nanoparticles have been introduced into chemically synthesized Putranjiva oil in a proportion that is tribologically assessed. The test was conducted using a pin on a disk tribometer, taking into account various conditions. Depending upon the specified concentration of silicon oxide nanoparticles, blends of lubricating oil nanoparticles have been distributed equally via the ultrasonication process. The different proportions of silicon dioxide nanoparticles were added to the chemically modified Putranjiva oil and tested for tribo-mechanism. Throughout the flow functioning review, all lubricant specimens demonstrate Newtonian characteristics by showing a direct correlation between shear rate and shear stress. Under the context of the exploration, a 0.6% magnitude of silicon oxide nanoparticles showed a decrease in the coefficient of friction and the wear rate. The scanning electron microscope pictures display improved surfaces immediately after the nanoparticle has been applied up to 0.6% concentration that was because of adhesion impact. The optimum level application was observed at 0.6% concentration to the epoxidized oil.

In tablet manufacturing, mixing operations in tumble blending (TB) and in the feed frame (FF) of the rotary press can both increase lubricity, negatively influencing the tablet mechanical strength. While the TB-driven lubrication was systematically studied, no reliable bench-scale methods exist for the effect of FF lubrication. Because TB and FF mixing are usually two successive operations in tablet manufacturing, we developed a phenomenological model to incorporate the impact of TB-driven lubrication and the FF lubrication on the tablet tensile strength (TS). We noted that exponential decay functions can describe the evolution of the tablet TS as the function of the extent of TB, as well as the residence time in FF. Hence, the overall lubrication sensitivity can be modeled by incorporating two distinct exponential decay functions. The model can be calibrated through bench-scale experiments. Using an investigational powder blend, we showed that this approach accurately predicted the tablet TS in a scale-up tablet compression study, thereby verifying its utility. This model can serve as a scale-up diagnostic and risk-assessment tool, with the ability to adjust the overall effect of lubrication by changing the TB scale and the FF residence time commensurate with the large-scale operations.

The thin film structures and tribological properties of aqueous solutions of a silicone-based amphiphilic block copolymer, bis-isobutyl polyethylene glycol (PEG)-14/amodimethicone (BIPA) copolymer, confined between mica surfaces were investigated using the surface forces apparatus. Measurements were made for three BIPA concentrations (0.005, 0.05, and 0.5 wt%); the effect of concentration on the structures and properties was evaluated. The BIPA molecules had positive charges in the solutions and formed an adsorbed layer on a negatively charged mica surface. The static hard-wall thicknesses were within the range of 3.3–5.6 nm for the three concentrations. Applying sliding motions under load L further decreased the thickness. The minimum dynamic thicknesses were 2.4–2.7 nm for the three concentrations, indicative of sliding between two adsorbed BIPA molecular layers. The friction coefficients were on the order of 10−5 for the three concentrations; extremely low friction was obtained originating from the slippage of the fluid-like water layer between the adsorbed layers. All three concentrations exhibited good lubricity, but precise comparison implies some differences in the film structures and friction mechanisms. The details of the differences were discussed from the perspective of the dissolution states of BIPA in the solutions and adsorbed/sliding conformations. The thin film structures and tribological properties of aqueous solutions of a silicone-based amphiphilic block copolymer confined between mica surfaces were investigated using the surface forces apparatus. Experiments were performed for three copolymer concentrations; the effect of concentration on the structures and properties was evaluated. All the concentrations exhibited good lubricity (friction coefficient on the order of 10−5). However, precise comparison between concentrations revealed some differences in the molecular friction mechanisms, which were discussed from the perspective of the dissolution states of copolymers in the solutions and adsorbed/sliding conformations.

Prolonged use of tight-fitting PPE, e.g., by COVID-19 healthcare workers leads to skin injuries. An important contributor is the shear exerted on the skin due to static friction at the skin-PPE interface. This study aims to develop an optimised wax-oil lubricant that reduces the friction, or shear, in the skin-PPE contact for up to four hours. Lubricants with different wax-oil combinations were prepared using beeswax, paraffin wax, olive oil, and mineral oil. In-vivo friction measurements involving seven participants were conducted by sliding a polydimethylsiloxane ball against the volar forearms to simulate the skin-PPE interface. The maximum static coefficient of friction was measured immediately and four hours after lubricant application. It was found that the coefficient of friction of wax-oil lubricants is mainly governed by the ratio of wax to oil and the thermal stability and morphology of the wax. To maintain long-term lubricity, it is crucial to consider the absorption of oil into the PPE material. The best performing lubricant is a mixture of 20 wt% beeswax, 40 wt% olive oil, and 40 wt% mineral oil, which compared to unlubricated skin, provides 87% (P = 0.0006) and 59% (P = 0.0015) reduction in instantaneous and 4-hour coefficient of friction, respectively.

Ionic liquids (ILs) have recently attracted considerable attention in tribology owing to their unique physico-chemical properties and promising lubrication performance when used in a wide range of material pairs. The aim of this review article is to summarize recent advances in our knowledge related to the lubrication mechanisms of neat ILs, with a particular focus on nanoscale studies dealing with the behavior of ILs in the boundary lubrication regime. We first discuss the current state-of-the-art concerning the normal pressure-dependent lubrication mechanism of ILs and then focus on the dynamic behavior of ILs upon nanoconfinment. Finally, we summarize recent research efforts aiming to control the tribological response of ILs by changing the surface charge density, evaluate the effects of impurities on the lubricity of ILs, and shed light on the IL tribochemistry at small length scales. While the field of IL-mediated lubrication has made significant progress, several open questions still remain, including the effects of temperature, impurities, and surface roughness on the friction response and dynamic behaviors of nanoconfined ILs. Additionally, a mechanistic understanding of the tribochemical reactivity of ILs is still lacking. To harness the full potential of ILs for tribological applications, significant work is still required to establish links between the IL structure, lubrication mechanism(s), and performance. These advancements will be instrumental for the predictive design, development, and implementation of ILs with enhanced tribological properties in next-generation lubricants for a variety of applications across several sectors, including manufacturing and transportation.

Adsorption of drug powder is caused by triboelectrification on the surface of starch capsule during filling process. Furthermore, high wear rate and poor water lubricity also hinder the further practical applications of traditional starch capsule. To solve these problems, a glycerol-modified starch capsule with perfect anti-triboelectrification and enhanced lubrication performance was fabricated. Hydrogen bond between glycerol and starch molecules could reduce the bound water content on the capsule surface and thus realizes anti-triboelectrification. By adding glycerol, a three-tier structure composed of starch-glycerol-water is formed through hydrogen bonding on the surface of the starch film, which has been proven to be favorable for lubrication performance. When 5% glycerol is added, the short-circuit current (Isc) of starch-based triboelectric nanogenerator (TENG) is reduced by 86%, and the wear volume of the starch film is reduced by 89%. Under water lubrication condition, the lubrication performance of the starch-glycerol film can reach the super lubricated level with a friction coefficient of about 0.005. This work provides a new route to obtain modified starch capsules with improved anti-triboelectrification property, reduced wear rate and superlubricity property.

Diamond-like carbon (DLC) has recently attracted much attention as a promising solid-state lubricant because it exhibits low friction, low abrasion, and high wear resistance. Although we previously reported the reason why H-terminated DLC exhibits low friction based on a tight-binding quantum chemical molecular dynamics (TB-QCMD) simulation, experimentally, the low-friction state of H-terminated DLC is not stable, limiting its application. In the present work, our TB-QCMD simulations suggest that H/OH-terminated DLC could give low friction even under high loads, whereas H-terminated DLC could not. By using gas-phase friction experiments, we confirm that OH termination can indeed provide much more stable lubricity than H termination, validating the predictions from simulations. We conclude that H/OH-terminated DLC is a new low-friction material with high load capacity and high stable lubricity that may be suitable for practical use in industrial applications.

One of the biggest difficulties with water-based drilling fluids for shale horizontal wells is its relatively high friction, especially for long horizontal wells. Improving the lubricating ability of drilling fluids is very important for expanding the extension range of horizontal wells in unconventional oil and gas wells. In this work, three kinds of lubricants, graphene oxide (GO), choline chloride/glycerol deep eutectic solvent (Gly-DES), and GO/Gly-DES, were synthesized to investigate their ability to improve the lubricity of water-based drilling fluids. These synthesized lubricants were all environmentally friendly. The tribological test and the filter cake adhesion coefficient test were used to compare the lubricity of these fluids. On the other hand, the traditional commercial lubricant solid graphite (HY-202) was taken as the reference sample. The results indicated that GO and Gly-DES can exert a more obvious lubricating effect at much lower concentrations compared to the reference sample. GO (0.25 wt %) can reduce the adhesion coefficient of filter cake by 93.33% and the friction coefficient of drilling fluid by 48.47%. The complex of GO and Gly-DES can further increase the reduction rate of adhesion coefficient and friction coefficient. Whether it was in reducing the adhesion coefficient of the filter cake or the friction coefficient of the drilling fluids, the combined lubrication effect of GO and Gly-DES was significantly better than using GO or Gly-DES alone. GO and Gly-DES decreased the coefficient of friction due to their good ability in producing a strong protective film on the contacting surfaces of the metal and filter cake. GO and Gly-DES can slightly reduce the filtration volume of drilling fluids and are suitable for shale water-based drilling fluids.

The optimization of cylinder surface topography draws immense amounts of researches, since it has far-reaching effects on engines’ overall performances. In order to promote the lubricity of ring/bore interface, the present study developed the multidimensional laser surface texturing (MLST) process, which fabricates controllable arrays of micro dimples on cylinder surface. The MLST process was achieved by a series of innovations, including its hardware and software systems, and optimization of process parameters and efficiency. A post-process was developed based on the finishing honing process to remove the recast bulges (RCB) induced by laser ablation. Additionally, the cylinder liners with different surface texturing schemes were bench tested on a single cylinder diesel engine. The experimental results indicated that near TDC (top dead center) region and piston skirt contacting region (SKIRT) were two high-impact regions for the technical efficiency of the MLST process. Benefiting from the reasonable optimization of oil distribution and enhanced hydrodynamic lubrication, the MLST process was able to reduce engine oil and fuel consumptions simultaneously. This paper provides a comprehensive introduction of equipment, pre- and post-process, and capacities of the newly developed surface modification technology.

The object of study is natural oils. Lubricating additives based on natural substances – vegetable oils and animal fats – meet the increased requirements for environmental safety of materials used in the drilling process. Consumption of environmentally friendly lubricants is constantly growing and requires an expansion of the raw material base for their production.Therefore today lubricants are important drilling reagents. From the ecological point of view, lubricating additives based on vegetable oils are of the greatest interest. The main physicochemical properties of sunflower and castor vegetable oils and the influence of these lubricating additives on lubricating and rheological characteristics of drilling fluids were investigated. In addition, the main properties of water-clay drilling fluids were investigated and their main parameters were determined according to standard API methods. During the testing of the samples, we took into account, first of all, a shear rate of the filter cake (CFC). It is the value that characterizes the strength of filter cake and is determined by the ratio of strength necessary for the tangential displacement of cyclic load across the cake to its weight. It is the CFC that characterizes the lubricating properties of the samples of solutions with a lubricant additive of a certain concentration that were studied.It is the CFC that characterizes the lubricating properties of the samples of solutions with a lubricant additive of a certain concentration that were studied. Based on the above studies, it can be concluded that the addition of castor oil effectively reduces the coefficient of friction of the filtration crust formed from the studied drilling fluids (fresh, mineralized, and saline). The recommended concentrations of this oil to the drilling fluid are 0.5 %, 1 %, and 5 %. Sunflower oil has an effective effect on the saline solution, less effectively – on the mineralized with an oil concentration of 0.5 %, 3 %, and 5 %. On the basis of the conducted researches the prospects of use of sunflower and castor oils at development of a new compounding of a greasing additive to a drilling mud are defined. Further research is aimed at assessing their lubricity in the drilling fluid at the friction limit «metal-metal». It is planned to repeat the study at the Sticking Tester OFI (USA).

While the methyl ester structure in biodiesel is responsible for lubrication improvement in base fuels with poor lubricity properties such as ultra-low sulfur diesel and non-upgraded HVO, relatively little is known about its effect on all-level blends, which would provide higher energy security for biodiesel utilization. In this study, binary blends of palm oil biodiesel (POB) with commercial petroleum diesel fuel (DF) and HVO at every 10%-v/v blend point were analyzed using a high-frequency reciprocating rig (HFRR) according to the standard method of ASTM D6079. It was found that the addition of POB successfully improved the lubricating properties of DF-CN48 and DF-CN51 and efficiently acted as a lubricity improver that showed a minimum friction coefficient and improved the specific wear rate. The adsorption of ester molecules on the metallic surfaces acted as a protective layer during the rubbing process, resulting in lubricity improvement for the diesel fuel. Interestingly, the 60–90%-v/v POB blend with HVO showed a lubricity capacity that competed determinatively and attractively, resulting in a non-ideal contribution to the changes in the friction coefficient, WSD formation, and specific wear rate.

Biodiesel is a renewable, clean-burning diesel replacement that can be used in existing diesel engines without modification. Biodiesel is among the nation's first domestically developed and economically usable advanced biofuels. Throughout the field of biodiesel including FAME/FAGE diesel variants, the concentrations of close to around 20% conform to every requirement out from the existing fuel content guidelines. Larger blending ratios are essential for hydrotreated vegetable oil blends to lubricity enhancers. Of organic biobutanol blends, the suggested blending ratio is restricted to 10% or less to prevent high water content and low cetane content. Here, the presented survey intends to make a review of 65 papers that concerns with biodiesel blends. Accordingly, systematic analyses of the adopted techniques are carried out and presented briefly. In addition, the performances and related maximum achievements of each contribution are also portrayed in this survey. Moreover, the chronological assessment and various blends of biodiesel in the considered papers are reviewed in this work. Finally, the survey portrays numerous research problems and weaknesses that may be helpful for researchers to introduce prospective studies on biodiesel blends.

The desulphurization process of diesel fuel is carried out to reduce the amount of SO2 emissions that can cause acid rain. However, the desulphurization process in diesel fuel not only removes the sulfur compounds but polyaromatic and polar compounds are also eliminated during this process. The loss of these two compounds can reduce the lubricity properties of diesel fuel. Therefore, it is necessary to add an additive compound that can increase the lubricity properties. In this research, 2-hydroxyethyl ester (HEE) was synthesized as an additive to increase the lubricity of diesel fuel. This compound was synthesized through the transesterification reaction of soybean oil and ethylene glycol with K2CO3 as the base catalyst. The composition of the synthesized additives was analyzed using the Gas Chromatography-Mass Spectrometry (GC-MS). Based on the results of GC-MS spectrum analysis, it is known that the 2-hydroxyethyl ester compound has been formed with a yield of 66.5% (relative to the area of the chromatogram peak). The HEE compound obtained is a mixture of 2 hydroxyethyl palmitate, 2 hydroxyethyl linoleate, 2 hydroxyethyl stearate, 2 hydroxyethyl arachidonate, 2 hydroxyethyl nervate, and 2 hydroxyethyl behenate.

Biodiesel, referred to as the monoalkyl ester of long-chain fatty acid ester that is synthesized by the complete transesterification of triglycerides, has captured the attention of drilling researchers attributing to its magnificent characteristics such as the high flash point, excellent lubricity, nontoxicity, high biodegradability, and abundant feedstock resources, which make it ecofriendly and technically and economically feasible for a sustainable drilling operation. There are several studies that reported and documented the usage of biodiesel in drilling fluids on laboratory and field scales. In this paper, the production and the key physical and chemical properties of biodiesel are thoroughly reviewed. Moreover, the applications of biodiesel in drilling muds either as base fluids or additives were comprehensively surveyed. The literature review revealed that the challenges of biodiesel applications in drilling mud systems are related to its chemical reactivity and adverse interactions with some additives, along with its performance deficiency at temperature above 120°C. Therefore, further investigation on temperature stability and additive compatibility is recommended. In addition, as a new approach, it is recommended to study the potentiality of using crude waste oils in drilling mud formulations. The lessons learned and recommendations stated in this paper will assist in enhancing the proved use of biodiesel and drilling fluid optimization.

The micro-arc oxidation (MAO) coatings were prepared in four different electrolyte systems, including mixed acid, phosphate, phosphate-aluminate and phosphate-silicate electrolytes. The friction and wear properties of MAO coatings in ambient air, seawater and four groups of saline solutions related to seawater were investigated. The results showed that the addition of silicate to phosphate could increase the density of the coating. The phosphate-aluminate ceramic layer exhibited the lowest wear rate in various environments. Additionally, the friction coefficient and wear rate of MAO coating in seawater were lower than those in ambient air, which was due to the boundary lubrication effect of seawater. Meanwhile, the presence of divalent metal salts in seawater made its lubricity better than other salt solutions.

Graphene is well-known as one of the best solid lubricants for its superlubricity and high mechanical strength. Weak adhesion leading to low interfacial compatibility is a significant challenge of ...

In this work, we carefully designed and synthesized a series of novel polyelectrolyte-functionalized carbon dots (CDs-PEI-X) by a facile and reversible phase transfer method based on the protonation reaction and anion exchange process executed on the surface of polyethylenimine-grafted CDs (CDs-PEI), where X denotes the anionic moieties of polyelectrolyte shells including hexafluorophosphate (PF6-), bis(trifluoromethane)sulfonimide (NTf2-), oleate (OL-), and bis(salicylato)borate (BScB-), respectively. Attributed to the favorable compatibility of these anions and polyethylene glycol (PEG) molecules, the hydrophobic CDs-PEI-X displayed excellent dispersibility and long-term stability in PEG200 base oil. Subsequently, the tribological behaviors of CDs-PEI-X as the lubricant additives of PEG200 were systematically investigated. It was proved that the anionic moieties of the polyelectrolyte shells of CDs-PEI-X played a crucial role in regulating their tribological behaviors. Particularly, CDs-PEI-OL was confirmed as an optimal additive, exhibiting the best lubricity, outstanding load-bearing capacity, long service life, and remarkable operational stability under boundary lubrication regime. Based on the tribological evaluations and worn surface analyses, the lubrication mechanism of CDs-PEI-OL was mainly attributed to the formation of the organic-inorganic hybrid adsorption film, the protective tribofilm, and its nanolubrication functions as scrollable "ball-bearing", i.e., the synergistic lubrication effects of surface polyelectrolyte shells and carbon cores. This study provides a feasible and versatile strategy to rapidly and effectively tailor the surface chemistry of CDs and discloses the essential contribution of carbon cores and surface groups on the lubrication process, which facilitates the development of advanced CDs-based nanolubricant additives.

The microencapsulation technique has been proven as a powerful and flexible tool to design and develop a multifunctional additive for various applications. The significant characteristics of this technique center around the ability to control the release of the core active ingredients by tuning the porosity and the permeability of the shell. However, this original concept has faced a major roadblock in lubricant research since it causes a major breakage of the microcapsules (∼70%) under severe stressed-shearing conditions. The shell fragments generated from such unwanted events significantly influence the friction and wear performances of the counterpart, thus limiting the ongoing research of the microencapsulation technique in tribology. To solve such technical bottlenecks, we develop a new strategy of utilizing the microencapsulation technique which focuses on the smart responsiveness of the shell with the base lubricant and the synergy between the incorporated materials. In this study, the smart-responsive colloidal capsule has been developed based on our proposed concept that demonstrates outstanding performances in improving the lubricity of the conventional melt lubricant (by ∼70%) under hot metal working conditions. An unprecedented oxidation-reduction (by ∼93%) and the first instance of ultralow friction (0.07) at elevated temperatures (880 °C) have been initially achieved. This work opens a new avenue of customizing a multifunctional additive package by utilizing the smart colloidal capsules in lubrication science.

Based on the preparation of magnetorheological fluids, material selection, proportioning method, and stability principle, this paper has conducted in-depth research on its friction and wear property. Firstly, the wear mechanism of magnetorheological fluids is analyzed theoretically. Secondly, an orthogonal test of magnetorheological fluid configuration with 6 lubricating additives of different types(oleic acid, hydrogenated castor oil, Teflon, boron nitride, molybdenum disulfide, graphite) and different mass fractions(0.5%, 1%, 1.5%, 2%) was done and the friction and wear property of magnetorheological fluids under different lubricants were compared. Finally, by analyzing and evaluating the experimental data, the general rule of lubricity additives used in the formulation of magnetorheological fluids with excellent performance was summarized, and the formulation of magnetorheological fluids with superior performance was obtained.

This research aimed to investigate the lubricity and wear properties of ultra-low sulfur diesel fuel (ULSD) blended with biodiesel and doped with biodiesel-based organic compounds. In this work, neat n-dodecane served as a surrogate for ultra-low sulfur diesel fuel (ULSD), Fischer Tropsch, and renewable diesel fuels. Additionally, some pure hydrocarbons were also investigated for unsaturation and carbon chain length. Tribological characterization was conducted on quenched and tempered AISI 4140 steel, substituting diesel fuel pump material, and using the ball-on-disc technique. The wear rates of biodiesel samples were about 2–4 times less than the vegetable oils. Esterification improves the lubricity of vegetable oils. The wear rate of biodiesel is about 5–7 times greater than that of fossil base commercial Eurodiesel fuel. Using biodiesel as an additive had a significant effect on the lubricity of pure n-dodecane, adding 2 wt% biodiesel resulted in 5–7 times wear rate reduction that equivalent to the lubricity level of commercial Eurodiesel fuel. Wear rates of pure hydrocarbons showed that wear is reduced with increasing chain length and unsaturation.

Dilution of diesel/biodiesel fuel with n-butanol in engines has a significant role in reducing the pollutants and improving the performance of compression ignition engines. This can be achieved using microfluidic networks, which allow an optimum dilution ratio to be precisely defined in an automated and controlled manner. This paper presents a novel, comprehensive study for such a process. The dilution profile of n-butanol-diesel/biodiesel fuel blends in a microfluidic hierarchical network system was predicted at different conditions. An analytical model was provided for the prediction of the variables’ distribution within the network. The model allowed for a wide range of n-butanol-diesel/biodiesel blends dilution to be investigated and validated experimentally and with CFD simulations. The mathematical model proved successful, returning precise results. Excellent agreement was found with the real data for the distributions of the variables within the network including the volume fractions, viscosity, and density. It showed that mixing 10 vol% with 90 vol% of n-butanol in diesel fuel resulted in maximum deviations of: 0.037% and 0.061% in the volume fractions of outlet streams; 0.19% and 0.08% in the density, and 2.32% and 14.13% in the viscosity, from the experimental and CFD simulation results, respectively. In addition, finer dilution of 30 vol % n-butanol in diesel fuel with 10 vol% n-butanol in diesel fuel showed maximum deviations of 0.006% and 0.08% in the volume fraction, 0.018% and 0.008% in the density, and 2.86% and 14.27% in the viscosity distribution, from the experimental and CFD simulations, respectively. The network’s performance with n-butanol-biodiesel blends compared with n-butanol-diesel blends was also presented. This study is of great importance for optimizing alcohol ratios in diesel/biodiesel for the best engine performance and minimum greenhouse gas emissions. It also allows for predicting the properties of un-experimented ratios of blends. Possible applications of this study include areas where precise control of the additives to diesel/biodiesel has a significant effect such as improving the lubricity in an engine, monitoring the fuel droplets, and/or precisely specifying the fuel spray characteristics.