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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.

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.

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

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.

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.

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 ...

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.

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.

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.

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.

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.

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.

Metalworking fluids (MWFs) lubricate, reduce forces and surface finish, and remove heat and swarf from the cutting zone. Lubricity additives influence wear and forces by reducing friction and preventing seizure. Additives(mineral oil, phosphate ester (P-ester), and dialkyl pentasulphide) were assessed for their machinability performance during Ti 6-4 milling with tungsten carbide(WC) endmills to establish life and cutting force coefficients (CFCs).P-ester additive provided the best performance;dialkyl pentasulphide(DPS) the lowest;CFCs varied with each additive; and a strong correlation was observed between Kte and life. The potential for accelerated MWF testing was outlined.

Room Temperature Ionic Liquids (RTILs) attract significant interest in nanotribology. However, their microscopic lubrication mechanism is still under debate. Here, using non-equilibrium molecular dynamics simulations, we investigate the lubrication performance of ultra-thin (0.5 GPa, while bi-layers sustain pressures in the 1–2 GPa range. The compression of these films results in monolayers that can sustain loads of several GPa without significant loss in their lubrication performance. Surprisingly, in such ultra-thin films the imidazolium rings show higher orientational in-plane disorder, with and the rings adopting a tilted orientation with respect to the gold surface. The friction force and friction coefficient of the monolayers depends strongly on the structure of the gold plates, with the friction coefficient being four times higher for monolayers confined between Au(100) surfaces than for more compact Au(111) surfaces. We show that the general behaviour described here is independent of whether the metallic surfaces are modelled as polarizable or non-polarizable surfaces and speculate on the nature of this unexpected conclusion.

Polyvinyl alcohol (PVA) is an organic polymer that is non-toxic, harmless to the human body, and has good biocompatibility. Polyethylene glycol (PEG) is a polymer that has good lubricity and compatibility. The unique graphite structure of carbon fibers can promote the potential application of carbon-fiber composites in tribology. This study explores the relationship between two kinds of organic polymer compounds and carbon fiber cloth (CFC), specifically a PVA/PEG composite coating that is impregnated on the CFC surface. The CFC is synthesized by chemical cross-linking, and the CFC composites (PVA/PEG/CFC) were synthesized. The tribological properties of PVA/PEG/CFC were tested under different concentrations, loads, and velocities. The effects of the different lubricants, surface morphologies, and tensile strengths on the mechanical and tribological properties of PVA/PEG/CFC were studied. In comparison to the original CFC, the friction coefficient and wear morphology of the composite material were reduced and the friction coefficient trend was stable. The addition of PVA/PEG improved the surface lubrication performance of the composite material and reduced the average friction coefficient. In addition, under the different lubrication mechanisms, oil as a lubricant can significantly reduce the friction coefficient and surface wear. In summary, the biocompatible coating process that is proposed in this study can effectively improve the tribological properties of the surface of the CFC.

Silicone hydrogels (SiHy), represent composite matrices composed of hydrophobic gas permeable silicone (Si) rich core and a surface enriched with hydrophilic polymer moieties. Their utilization in contact lens design requires number of SiHy properties (hydration, wettability, lubricity) to be optimized for the challenging conditions at the ocular surface. Typical limitations in literature are that (i) these properties are studied in isolation, monitoring only one parameter but not the rest of them, and (ii) measurements are performed with hydrated samples immediately after removal from storage solutions. Here we study the simultaneous evolution of critical material properties (evaporative loss of water, water contact angle, coefficient of friction) of different SiHy subjected to continuous blink-like desiccation/rehydration cycling. SiHy with wetting agents incorporated in their core (narafilcon A, senofilcon A) were particularly susceptible to extended desiccation. Stenfilcon A, a material with only 3% bulk Si content maintained its performance for 4 h of cycling, and delefilcon A (80% surface water content) resisted extended 8 h of desiccation/rehydration runs. Strong correlation exists between the evolution of SiHy wettability and lubricity at ≥4 h of blink-like cycling. Understanding the interplay between SiHy properties bears insights for knowledge based design of novel ophthalmic materials.

The current study is devoted to the use of vegetable-oil fatty acids (FAs) as lubricity additives for modern diesel fuels with ultra-low sulfur contents. The effectiveness of liquid castor, linseed, coconut, and sunflower oils in the base components of diesel fuels for hydrotreating, hydrocracking, and hydroisomerization is comparatively evaluated. It is established that all investigated vegetable-oil FAs are effective anti-wear additives as compared to a commercially available additive while FAs of castor oil, which consist of 90% ricinoleic acid, are most effective as anti-wear additives.

The supersaturated saline drilling fluid (SDF) with strong inhibition, as a novel alternative to anhydrite formation drilling, is crucial for the safe and economic drilling operation. In this work, a high performance supersaturated SDF was experimentally formulated in terms of the long anhydrite features of Missan Oilfields. Composite weighting approach involving liquid and solid materials was introduced to reinforce the inhibition of supersaturated SDF. A suite of laboratory tests was conducted to screen the essential viscosifiers and filtrate reducers, and optimize the formula of supersaturated SDF, by means of evaluating the basic rheological and filtration properties. The results showed that univalent salts, NaCl, KCl, and HCOONa, are utilized to formulate the multiple brine phase, and polymeric additives, VIS and S-FLO, can effectively improve rheology and filtration properties. The newly developed supersaturated SDF exhibits the excellent thermal stability, lubricity, as well as inhibition capability, which should be an instructive solution to minimize the hole problems in the anhydrite drilling.

In the present work, two types of novel nano additives, titanium sulfonate ligand/black phosphorus (TiL4/BP) and titanium dioxide/black phosphorus (TiO2/BP) nanocomposites, were prepared. The tribological behavior of the steel/steel friction pairs lubricated by polyalphaolefins type 6 (PAO6) containing the nanocomposites under boundary lubrication was studied. The worn surfaces were analyzed using modern surface techniques. The experimental results show that the rubbed surfaces became smooth and showed little wear with the addition of the nanocomposites. TiO2/BP nanocomposites can significantly improve the lubricity of BP nanosheets under high contact stress. The synergistic roles of the load-bearing abilities and rolling effect of TiO2 nanoparticles, the slip induced by the BP with its layered structure, and the establishment of a tribofilm on the sliding interface are the basis of the tribological mechanisms.

Constructing a slippery lubricant-infused surface (SLIS) whose internal microstructure and surface properties can be fully repaired helps to improve its property stability and extend technological implications but has presented a huge challenge. A class of fully repairable slippery organogel surfaces (SOSs), which uses microstructured paraffin as reconfigurable supporting structure and silicone oil as lubricant dispersion medium, is reported here. Attributed to nearly 90 wt % of silicone oil stored in the slippery organogel system and good compatibility with the paraffin-based framework, SOSs combine continuous lubricity and reliable lubricant storage stability. Furthermore, the thermally sensitive paraffin-based framework can quickly switch between solid supporting structure and liquid solution according to the ambient temperature, thereby achieving rapid regeneration of microstructure. This unique system consisting of reconfigurable framework and flowable lubricant derives two types of repairs aimed at varying degrees of damage. Significantly, the easy-to-prepare SOS, on the other hand, allows the adoption of various substrate surfaces for different purposes to form an antiadhesion coating and exhibits excellent antistain, antialgae, and anti-icing performance, thus greatly improving the flexibility of such materials in practical applications.

Appropriate amount of methyl myristate (C14), methyl palmitate (C16), methyl stearate (C18), methyl oleate (C18:1), methyl linoleate (C18:2), and methyl ricinoleate (C18:1OH) were blended into low-...

The present study investigated oxidation reactivity and hot lubricity of a sodium silicate melt at different Na2O/SiO2 ratios under elevated temperature stimulation. Static oxidation prevention was achieved at 920 °C when the Na2O/SiO2 ratio reached 1:3 (trisilicate) and 1:2 (disilicate), but it started to deteriorate in the case of 1:1 (metasilicate). At a high concentration of sodium (metasilicate), a severe corrosion reaction between the melt and oxide took place that resulted in a composite coating on the steel substrate. This high-temperature reaction accelerated the formation of ionic charges from the steel base and promoted oxidation. However, friction and wear reduction is proportional to an increase in the sodium oxide fraction. Metasilicate (1:1) exhibited excellent lubricity under the hot frictional test at 920 °C compared to other lubricants. It was due to the formation of the sodium-saturated surfaces and an amorphous silica layer, which was associated with the high-temperature reactivity of sodium toward the oxide surface. In addition, the NaFeO2-Fe2O3 composite film, as the reaction product of individual sodium charge and oxide, plays a significant role in maintaining the tribofilm stability for metasilicate, which was not present for disilicate. This study advances the understanding of how sodium-containing compounds perform oxidation prevention and generate lubricity at hot rubbed surfaces.

Ni–based composite coatings with different amounts of TiO2–ZnO were fabricated by atmospheric plasma spraying (APS) to protect GH4169 superalloy substrates against excess wear and friction at elevated temperatures. In addition, the influence of the simultaneous addition of the oxides on the microstructure, microhardness, and wear behaviour was investigated. According to the results, the simultaneous addition of TiO2/ZnO provides anti-friction and wear inhibition over 600 °C. In particular at 800 °C, the TiO2–ZnO/Ni–5wt.%Al composite coating (10 wt% TiO2 and 10 wt% ZnO were incorporated within Ni–5wt.%Al matrix) exhibits a superior lubricity and wear resistance compared to the Ni–5wt.%Al based coatings. The XRD, Raman, and TEM characterisations reveal the formation of a glaze oxide layer consisting of NiO, TiO2, ZnO and the in-situ production of ternary oxide (Zn2TiO4), which was primarily responsible for the tribological performance of the sliding wear contacts at the specific temperature.

Atomic force microscopy has been used to measure the lubricity of a series of ionic liquids (ILs) at mica surfaces in the boundary friction regime. A previously unreported cation bilayer structure is detected at the IL-mica interface due to the formation of H-bonds between the hydroxy-functionalized cations [(c-c) H-bonds], which enhances the ordering of the ions in the boundary layer and improves the lubrication. The strength of the cation bilayer structure is controlled by altering the strength of (c-c) H-bonding via changes in the hydroxyalkyl chain length, the cation charge polarizability, and the coordination strength of the anions. This reveals a new means of controlling IL boundary nanostructure via H-bonding between ions of the same charge, which can impact diverse applications, including surface catalysis, particle stability, electrochemistry, etc.

In connection with the limited resources of fossil fuels and the reduction of emissions and stimulation of agricultural areas, a very important indication is the search for alternative fuels – biofuels. The article presents the results of testing the lubricating properties of selected fuel mixtures. The lubricity of diesel fuel (DF), DF with 7% content of methyl esters of rapeseed oil fatty acids (RME), technical linoleic acid and DF with 7% content of RME and 10% content of technical linoleic acid was tested. The research was carried out on the author's research stand in the amount of 20 dm3 of mixture. Four parameters were taken into account: mass loss of samples, the footprint area of cooperation, diameter of equivalent wheel and average value of the coefficient of friction. It has been shown that the addition of linoleic acid to diesel fuel containing RME causes a significant increase in the mass loss of the samples and the footprint area of cooperation as well as its diameter of equivalent wheel, during lubrication with such a mixture. As a result of the addition of linoleic acid, no positive results were obtained, as the lubricating properties in this case deteriorated. Therefore, it is justified to continue looking for fuel additives that will eliminate this negative effect.

The paper presents the tests results of lubricity properties of base greases, containing hexagonal boron nitride (h-BN). To conduct the required tests, a four ball machine was used. This device is commonly used when assessing lubricity properties of oils and greases. The following normative lubricity parameters were defined: welding point Pz [daN], the value of last non-seizing load Pn [daN], seizing at smoothy growing load Pt [daN], as well as the wear limiting capacity load Goz [daN/mm2]. Furthermore, several non-normative tests were completed that covered indication of two parameters making it possible to complete an assessment of lubricity properties of oils. Based on the conducted research, it was found that hexagonal boron nitride is an additive that improves the lubricating properties of the base grease. The best effects of the improvement, taking into account the adopted tribological criteria, were noted for a sample containing 10% (m/m) hexagonal boron nitride with an average grain diameter of 65÷75 nm. It was found that the lower granulation of the additive (h-BN) positively influences the efficiency of the grease lubrication of the base, under the conditions of tests on a four-ball model apparatus. Keywords: tribology, lubricity, boron nitride, greases

Lubricating oil producers are shifting attention toward the use of renewable and biodegradable energy sources for the production of lubricating oils. This is necessitated by the depleting mineral based energy sources and the negative impact of continuous usage of engine oils from fossil sources. Biomass sources are cheap, environmentally friendly, and offer a good alternative to the conventional mineral oil sources. Biolubricants provide lubricity for two moving-surfaces in contact. They are essential for heat transfers, power transmissions, lubrication, and corrosion inhibition in machinery. However, the use of biolubricating oils are associated with challenges such as poorer low temperature properties and poor oxidative stability during usage. Chemical modification of vegetable oils with polyols has been explored as a potential source for biolubricant synthesis and production. This paper provides a concise review of the use of trimethylolpropane (TMP) as the polyol used for chemically-modified biolubricants using vegetable oils as base stocks. TMP improves the physicochemical properties of biolubricants and enhances the thermo-oxidative stability of the biolubricants. Keywords: Chemical modification, Biolubricant, Lubricating oils, Vegetable oils, Trimethylolpropane

In the present study, graphene nanoplatelets (GNPs: 1–2 wt. %) reinforced TiN coating were successfully fabricated over titanium alloy using a reactive shroud plasma spraying technique. All coatings were completely oxide free, while the addition of GNPs suppressed the non-stoichiometric TiN0.3 phase. Improvement of 19%, 18% and 300% in hardness, elastic modulus and fracture toughness was achieved by mere addition of 2 wt. % GNP. The addition of GNP in TiN also reduced the wear volume loss and the wear rate of the coatings for the entire range of temperature (293–873 K). Moreover, GNPs also manifested the coefficient of friction (COF) of the coating. Post wear characterization revealed that the presence of GNP throughout the wear track even at 873 K. The multi-layer structure of GNPs assisted in long term lubricity to the surface and increased the wear resistance of the coating.

Reduced emissions and environmental burden from shipping are an important aim of tightening emission regulations and ambitious climate change strategy. Renewable methanol produced from biomass or from other renewable sources represents one option to face these challenges. We studied the potential of renewable methanol to offer such benefits in diesel operation in a Scania ethanol engine, which is designed for additized ethanol fuel (ED95) containing ignition improver and lubricity additives. Methanol (MD95) with several types of ignition improver and lubricity additives was studied for use in diesel engines. MD95 fuels were clean-burning, emitting even less gaseous emissions than ED95, particularly when glycerol ethoxylate was used as an ignition improver. Particle mass and number emissions originating from additives in the experimental fuels could be reduced with an oxidation catalyst. Reduced additive dosing in the MD95 fuels was studied with the aid of fuel injection into the intake manifold. Overall, the results showed that the monofuel MD95 concept is a promising solution for smaller vessels equipped with 800-1200 kW engines. © (Less)

Introduction. The paper considers the evolution of friction coefficient of the pair of copper - steel alloy under friction in a hexanoic acid solution in various concentrations, and antiwear properties of the steel-steel friction pair in an oil-acidic medium. The work objective is to explore the effect of hexanoic acid additives on the tribological characteristics of friction pairs under the friction interaction in waterborne and paraffin-based formulations. Materials and Methods. Tribological studies of a brass-steel friction pair were carried out on the AE-5 end-type friction machine. Antiwear characteristics were explored on a four-ball friction machine (FBW) in accordance with the standard GOST 9490–75. When tested at the FBW, the objective parameters of the lubricity of the oiling compositions were: welding load (Рс); wear spot diameter (Dн), critical load (Рк). Roughness parameters of the servovite film were determined through the optical profilometry; its microgeometry and structure at the nanoscale – through the atomic force microscopy. Research Results. Tribological properties of the brass-steel tribocoupling in aqueous media and steel-steel one in petroleum paraffin-based media are studied. The dependence of the frictional characteristics of the brass-steel friction pair on the concentration of carboxylic acid is established. Its optimum concentration is specified, which provides the effect of wearlessness. A decrease in surface roughness is revealed as a result of the frictional interaction of a brass-steel friction pair in the hexanoic acid solution compared to the initial friction surface due to the formation of a sufficiently dense layer from fine-grained copper clusters with tight particle-size dispersion. The tribological characteristics of a steel-steel friction pair were found to depend on the composition of the lubricant. It is shown that the dependence of the size of the wear scar diameter (WSD) on the acid content in the base oil is nonmonotonic in nature with a pronounced minimum at a concentration of 0.1 mass. %. The critical load (Pк) at a content of 0.05 and 0.1 mass. % increases by 32%, welding load (Pc) - by 27%.Discussion and Conclusions. As a result of the tribological studies of a brass-steel friction pair in the hexanoic acid solution, it has been found that the optimum acid molar concentration in the lubricant composition is 0.1 mol/L. Under the frictional interaction of a brass-steel pair in the hexanoic acid solution, an antifriction copper film is formed on the friction surfaces, which contributes to a sharp decrease in the friction coefficient to 0.007 and metal wear of the friction pair to 25 times. As a result of the frictional interaction of a brasssteel friction pair in the hexanoic acid solution, a decrease in roughness is revealed compared to the initial friction surface. It is found that the frictional interaction of a brass-steel pair in the hexanoic acid solution causes a significant modification of the friction surface as a result of the deposition of finely dispersed copper clusters occurring in the lubricating medium composition and forming a servovite film. As a result of studies, it is found that the dependence of the WSD size on the acid content in the base oil is nonmonotonic in nature with a significant minimum at a concentration of 0.1 mass. %. It is shown that the addition of 0.1 mass. % of hexanoic acid into the lubricant composition exhibits the smallest wear of the steel-steel tribological pair, the WSD decreases to 0.497 mm, the critical load (Pк) and the welding load (Pc) increase by 32% and 27%, respectively.

Disposal of the petroleum lubricants creates problem through degradation of the environment. To address this issue, a substitute should be available which can provide the same properties available while considering petroleum lubricant. Calophyllum inophyllum is one of the feasible oil which is available in abundant quantity. In this study, Calophyllum inophyllum oil was undergone through the chemical modification process and after that tribological characterization was performed. The modified oil was blended with the mineral oil in certain ratios including 5–15% blend. Minimum COF was observed with 5% and 10% blends which gets increased with 15% blend application. Wear rate and wear scar diameter also shows the same behavior at all applied conditions. It can be concluded that up to 10% blend of modified Calophyllum inophyllum oil provides better lubricity with comparison to the mineral oil during all conditions considered.

For improving lubricity, the formation of zwitterionic polymer brushes on material surfaces is one of the most promising approaches. In this study, the photoreactive zwitterionic monomer 2-[2-(methacryloyloxy)ethyldimethylanmmonium] ethyl benzophenoxy phosphate (MBPP) was synthesized to improve the stability of zwitterionic polymer brushes. Although MBPP contains a benzophenone moiety in this molecule, it is water-soluble because of the zwitterionic linker. As a substrate, poly(ether ether ketone) (PEEK) was selected because it has recently been used to replace metals in orthopedic implants. Furthermore, PEEK is photosensitive, and UV graft polymerization of (meth)acrylic monomers on the surface can be performed without using any photoinitiators. Aqueous solutions containing various molar ratios of 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and MBPP were prepared, and the PEEK specimens were immersed in these solutions. UV light was used to irradiate the solutions for 180 min, and the formation of grafting layers of zwitterionic polymers on PEEK specimens was confirmed using contact angle measurement and X-ray photoelectron spectroscopy. The surface friction of PEEK was effectively reduced via the photopolymerization of zwitterionic monomers. However, the surface lubricity of poly(MPC) (PMPC)-grafted surface deteriorated during continuous friction because of the removal of PMPC from the surface. Nevertheless, the stability of polymer brushes was effectively improved by adding only 0.5-0.75 mol % of MBPP in the monomer solution. Moreover, the reduction of wear on the surface was determined using confocal laser microscopy. The excellent lubrication phenomenon was attributed to preserving the hydration state of grafted polymers under compressive stress. Moreover, bacterial adhesion on substrates was tested and observed on a neat PEEK and scratched regions of uncross-linked PMPC-grafted PEEK. Note that bacterial adhesion was completely suppressed on the surface of PEEK modified with cross-linked PMPC brushes with MBPP. Thus, we conclude that the surface modification of PEEK with MPC and MBPP can provide ideal surface properties for orthopedic devices.

This work has developed and evaluated a microemulsion-based drilling fluid formulation with characteristics to be applied in oil wells. The microemulsion was formulated with a solution of water/glycerol, pine oil, and Tween 80, a nonionic and biodegradable surfactant. The physical and chemical properties of the drilling fluid obtained in this work were investigated through rheology and filtration analysis, solids content, aging, lubricity, toxicity, and thermal degradation. A non-toxic microemulsion-based drilling fluid oil-in-water (O/W) with high lubricity (0.07638) and thermal stability was obtained with suitable viscosity, gel strength and low fluid loss (4.0 mL), low solids content (6%), stability in a wide range of salinity conditions, and the possibility of high water content (above 85% in mass fraction). The fluid presented a pseudoplastic behavior, and statistically significant Herschel–Bulkley parameters were obtained.

Water-glycerol as one promising alternative for mineral oil can be applied as a green lubricant but has poor lubricity and strong corrosivity. It is desirable to design multifunctional water soluble lubricant additives. Protic ionic liquids (PILs) show considerable potential due to their facile preparation and environmental friendliness. Herein, an eco-friendly PIL ([osar][mea]) was facilely prepared from an amino acid derivate and investigated its anticorrosion and lubrication performances in the glycerol solution. Furthermore, the wear traces were measured using SEM/EDS and XPS for exploring the lubrication mechanism. The prepared PIL can rapidly increase the corrosion inhibition ability of water-glycerol as its concentration increases over CMC, and the anion playing a key role in the light of DFT calculations. Furthermore, [osar][mea] can greatly enhance the lubrication capability especially of water-glycerol while its concentration in the glycerol solution exceed 3%. The lubricity reduced with the increasing load. By the means of using SEM/EDS and XPS evaluation of the wear traces, we can speculate the possible lubrication mechanism may be the presence of the [osar][mea] adsorption film and the tribofilm containing complex nitrogen compounds.

In this paper, the fuel properties of mixtures of diesel fuel and ethanol and diesel fuel and butanol in the ratio of 2.5% to 30% were investigated. The physicochemical properties of the blends such as the cetane number, cetane index, density, flash point, kinematic viscosity, lubricity, CFPP, and distillation characteristics were measured, and the effect on fuel properties was evaluated. These properties were compared with the current EN 590+A1 standard to evaluate the suitability of the blends for use in unmodified engines. The alcohols were found to be a suitable bio-component diesel fuel additive. For most physicochemical properties, butanol was found to have more suitable properties than ethanol when used in diesel engines. The results show that for some properties, a butanol–diesel fuel mixture can be mixed up to a ratio of 15%. Other properties would meet the standard by a suitable choice of base diesel.

This study relates to developing future alternative fuels and focuses on the effects of a fuel’s molecular structure on its properties and performance in advanced propulsion systems. The tribological performance of various biomass-derived oxygenated alternative fuels, including butanol, pentanol, cyclopentanol, cyclopentanone, and gasoline and their blends with diesel, was investigated. Lubricity tests were conducted using a high-frequency reciprocating rig (HFRR). Cyclopentanone-diesel and cyclopentanol-diesel blends result in smaller wear scar sizes compared to using their neat forms. A lower steel disc contaminated with the alternative fuels during the HFRR tests resulted in worn surface roughness values lower than those of the neat diesel by up to 20%. It is believed that these reductions are mainly due to the presence of the hydroxyl group and the carbonyl group in alcohols and ketones, respectively, which make them more polar and consequently helps the formation of the protective lubrication film on the worn moving surfaces during the sliding process. Overall, the results from this study indicate that environmentally friendly cyclopentanol and cyclopentanone are practical and efficient fuel candidates for future advanced propulsion systems.

Introduction/Purpose Vessel models are a first step in developing endovascular medical devices. These models are often madefrom glass or silicone, which do not accurately represent the mechanical properties of human vasculartissue, limiting their use to basic training and proof-of-concept testing. This study outlines methods toquantify the mechanical properties of both human vascular tissue and synthetic biomaterials for creatingrepresentative vessel models. Materials and Methods Human vascular tissue was assessed and compared to standard silicone and new UV-cured polymers (VC-A30). Vessel materials were characterized with eight mechanical tests: compressive, shear, and tensiledynamic elastic modulus, Poisson’s ratio, hardness, radial compression, compliance, and lubricity. Half ofthese testing methods were non-destructive, allowing for multiple mechanical and histologicalcharacterizations of the same human tissue sample. Results Histological evaluation of cellular and extracellular matrix of the human vessels showed the dynamicmoduli and Poison’s ratio tests were non-destructive (figure 1 Left), whereas the destructive hardnesstest created significant tearing of the vessel layers (figure 1 Middle). Fluid absorption by VC-A30 showedstatistically significant softening of mechanical properties, stabilizing after 4 days in phosphate-bufferedsaline (PBS). VC-A30 exhibited statistically similar results to human vasculature, with% error less than29%, in 5 of 8 mechanical tests, versus 1 of 8 for standard silicone. Human vessel lubricity (determinesdevice trackablility within a vessel) statistically matched the lubricity of all the VC-A30 samples (figure 1 Right). Conclusion VC-A30 provides a new option for creating translucent in vitro vascular models with anatomically-relevantproperties. VC-A30 can be formed into highly accurate models with specific mechanical properties usingthe latest 3D-printing techniques. These new vessel analogs may simulate patient-specific vessel diseasestates, improve surgical training models, accelerate the development of new endovascular devices, andultimately reduce dependencies on animal models. Disclosures K. Lewis: None. J. Vigil: None. N. Norris: None. W. Merritt: None. T. Becker: 1; C; NIH grant #5R42NS097069-03.

3D printing of a stiff and lubricative hydrogel-based meniscus substitute has been challenging since printability and stiffness compromise each other. In this work, based on an upgraded self-thickening and self-strengthening strategy, a unique multiple H-bonding monomer N-acryloylsemicarbazide (NASC) is firstly copolymerized with a super-hydrophilic monomer carboxybetaine acrylamide (CBAA) in dimethyl sulfoxide (DMSO)/H2O to form a soft poly(NASC-co-CBAA) gel, in which PCBAA serves to weaken the H-bonding interaction and avoid hydrophobic phase separation. The poly(NASC-co-CBAA) gel is then loaded with concentrated NASC and CBAA, followed by heating to form a thickening sol ink, which is printed into different objects that are further photoirradiated to initiate the copolymerization of entrapped NASC and CBAA, resulting in the formation of a high performance hydrogel with a Young's modulus of 10.98 MPa, tensile strength of 1.87 MPa and tearing energy of 5333 J m-2 after DMSO is completely replaced with water, due to the re-establishment of NASC H-bonds. Importantly, PCBAA affords high lubricity in printed hydrogels. The printed PNASC-PCBAA meniscus substitute can substitute rabbit's native meniscus and ameliorate the cartilage surface wear within a set 12-week time window, portending great potential as a meniscal substitute and other soft-supporting tissue scaffolds.

This study demonstrates a simple and multistep approach for a covalent functionalization of chemically-prepared graphene oxide (GO) using branched polyethylenimine (PEI) through nucleophilic addition reaction to prepare GO-PEI. Further layer-by-layer (LBL) assembly on functionalized GO-PEI with anionic polyelectrolyte, poly(acrylic acid sodium salt) (PAA) and poly(sodium 4-styrenesulfonate) (PSS) have been undertaken to fabricate polymer brushes (PB). The physicochemical structures of GO, GO-PEI and LBL assembled PB [GO-PEI-PAA and GO-PEI-PSS] have been explored using standard spectral and morphological analysis. The macrotribological results demonstrated that GO-PEI-PAA/GO-PEI-PSS (0.5 wt%) as paraffin oil dispersible additives significantly decreased the coefficient of friction (COF) and wear at different contact pressures of steel-steel tribopairs. The influence of contact pressure and load-bearing ability of the polymer-grafted GO as nanolubricants have been examined carefully. The COF of PB particles provided a reduction of 85% (low pressure, ∼0.9 MPa) and 66.65% (high pressure, ∼1.35 GPa) compared to lube paraffin oil and exhibited a lower specific wear rate (2.26 × 10-8 mm3 N-1 m-1) at macrotribological pin/ball-on-disc trials, revealing superior lubricity. The PB containing nanolubricants also exhibited high load-bearing ability (till ∼1000 N load, Pm ∼6.1 GPa) with considerably lower COF and wear, which were investigated using a four-ball tribotester. Among the functionalized polymeric GO particles, PSS polyelectrolyte containing GO-PEI-PSS showed better COF and wear reduction ability with extremely high load-bearing capacity due to the strong interfacial adhesion properties of PSS to generate strong protective synergetic lubricating tribofilm into the rubbing interfaces, which is comprehensively investigated by post-tribological analysis.

In this study, an investigation has been carried out to examine the tribological features of Rice bran oil (RBO) based biodiesel as an agent to improve lubricity. RBOB was successfully generated by...

Vapour compression systems are designed to use refrigerants and lubricants for smooth performance. However, recent advances in nanoparticles research have led to the use of Cu and Ag-nanoparticles (AgNPs and CuNPs) as compressor fluid modifiers. In this study, several concentrations of AgNO3 and CuSO4 solutions were adopted in synthesizing nanoparticles for use in a compressor oil. The optimum Coefficient of Performance and cooling effect of the system were observed at optimum concentrations of 0.08 and 1.6 M for the Ag- and CuNP- lubricating oils, respectively, thus giving better cooling effects than the ordinary Copeland 46B oil. At optimum conditions, the weakly acidic CuNP-oil performed better than the weakly alkaline AgNP-oil with cooling temperatures of −8 and 2.3 °C, respectively. Equilibrium concentrations for both particulate oils were found to be 0.08 and 2.7 M at the same yield stress of 2 lb./100 ft2, while the lubricities of the oils ranged from 0.119–0.154, 0.134–0.155 and 0.156–0.180 for the CuNP-, AgNP- and Copeland 46B oils, respectively. Since lower lubricities are indicative of better lubrication, it then implies that the CuNP-oils gave the best lubricities. An increase in the motor speed gave a corresponding increase in the torque generated as well as, the lubricity coefficients and lubricities of all the oils. Enthalpy changes ranged from 70.3–520 Jg/mol for the 1.1–2.1 M CuNP-oils, although, it was very high (4523.5 Jg/mol) for the 2.7 M CuNP-oil which may be due to the superficial distribution of copper as well as its large surface area to charge ratio at the oil surface, thus making it a better conductor of heat relative to the AgNP-oils. For the AgNp-oils, the enthalpy changes were very small i.e. from −1.012 – 1.2957 Jg/mol whereas, it was 523 Jg/mol for the Copeland oil. Furthermore, the least power consumption was obtained for the CuNP-oils.