Lubricants are an essential component in high-performance mechanical equipment, but traditional lubricants are becoming inadequate for meeting the increasing demands for anti-friction and anti-wear properties and they discharge harmful chemicals to the environment. The purpose of the present study was to explore the use of sepiolite as a novel oil additive to extend the performance of lubricants. Sepiolite nanofibers were first treated by acid followed by a dry air flow, aimed at increasing the pore volume and decreasing the particle size. Then the nanofibers were further modified by an organosilane coupling agent to reduce the surface free energy and to improve the dispersion stability in lubricant. A significant improvement in the performance of the lubricant was achieved by using the modified sepiolite nanofibers as an additive. When the amount of modified sepiolite nanofibers added was 1.5 wt.%, the best performance was demonstrated by the lubricant, showing a viscosity increase at 40°C and 100°C, and an increase in resistance to oxidation. Moreover, the acid value and pour point decreased, and the copper sheet corrosion level dropped to its lowest value.

Since ancient times, lubricants have been used to reduce friction and wear problems of mechanical systems. However, nowadays, there is a constant effort to improve their performance through additives so that they can accomplish properly in this modern world. In that sense, in this study, it was proposed the use of Poly(ε-Caprolactone) (PCL) as a biodegradable additive in Castor oil. The effect that this additive has on the tribological properties of AISI 4140 steel/Al2O3 tribosystem was analyzed. For this purpose, PCL was dissolved in Castor oil at 65 °C for 15 minutes. Later, once the lubricant formulations got into room temperature, friction tests were conducted with a ball-on-disk configuration. Several experiments were systematically carried out in order to study the factors that could influence the performance of the tribological system, for instance: additive concentration, velocity, temperature, and wear track radius. The kinetic friction coefficient was used to analyze the results as an output variable. The parameters in which the best friction behavior was observed were employed again to compare the efficiency of the polymeric additive by profoundly analyzing and comparing the wear response of the system. The PCL additive showed great results by decreasing friction up to 30% compared to the neat Castor oil. Nevertheless, as the opposite effect, this additive increased the steel wear to almost half an order of magnitude. Given the above, this investigation showed that, with further studies, Poly(ε-Caprolactone) could be used as an additive in vegetable oil-based lubricants for the improvement of friction performance.

The aim of this investigation was to study castor, canola, and sesame vegetable oils in order to evaluate their potential use as lubricants in steel mechanical components. For this purpose, densities of each oil were evaluated using the pycnometer method, as well as their dynamic viscosities through a Brookfield DV-II rotational viscometer. Both properties were evaluated at temperatures of 25, 40 and 100 °C. Additionally, viscosity indexes were determined according to ASTM D 2270. These rheological properties were used to estimate the lubrication regime considering parameters of real contact conditions in mechanical components. Friction and wear analyses were carried out to investigate the behaviour of the vegetable oil as lubricants. Such tests were carried out at room temperature on a CSM tribometer with pin-on-disk configuration by using castor, canola and sesame oils as lubricants. AISI 4140 hardened steel against AISI 100Cr6 steel pin was used as a mechanical component. From the rheological study, it was observed that canola and sesame oils behave as dilatant fluids at the evaluated temperatures, while castor oil behaves like a Newtonian fluid at 25 and 40 °C. Castor oil showed the highest density value among oils studied, but it also exhibited the lowest value of viscosity index (271). Contrarily, sesame oil was the least dense, but it exhibited the highest viscosity index (545). On the other hand, the lubrication regime study showed that by using castor oil as a lubricant in the mechanical component (4140/100Cr6), the system worked in a mixed lubrication regime while by using canola and sesame oils the system operated in boundary lubrication conditions. Finally, the kinetic friction coefficients were different for each lubricant obtaining the lowest value with castor oil while the highest value of friction coefficient was exhibited by the sesame oil lubricant.

The heat-assisted magnetic recording (HAMR) head–disk interface is a unique operating environment that combines nanoscale spacings, high shear rates, high-temperature gradients, and high optical fluxes in a mass-produced device. One of the greatest challenges is to develop materials for the head–disk interface that enable the required head–media spacing while also providing reliability. Traditional head–disk interface materials, engineered and optimized for conventional magnetic recording hard-disk drives, are challenged to provide the needed performance at the high temperatures that HAMR involves. We review some of the primary materials used in conventional magnetic recording, how high temperatures challenge their performance, and some of the current understanding and strategies to develop a reliable HAMR head–disk interface.

Greases are essential in the electrical industry for the purpose of minimizing wear and coefficient of friction (COF) between the components of circuit breakers. Nowadays some researchers have explored the addition of nanoparticles to enhance their tribological properties. In this study, tribological tests were performed on different greases employed for the electrical industry. CuO and ZnO nanoparticles were homogeneously dispersed into the greases, varying their concentration (0.01 wt.%, 0.05 wt.%, and 0.10 wt.%). A four-ball tribotest, according to ASTM D-2266, and a ball-on-disk tribotest, according to ASTM G-99, were performed in order to analyze the wear scar diameter (WSD), COF, wear mass loss and worn area. The worn materials were characterized with an optical 3D profilometer measurement system. Anti-wear properties were enhanced up to 29.30% for the lithium complex grease (LG) with no nanoparticles added, in comparison with the aluminum complex grease (AG), providing a much better tribological performance; in the ball-on-disk tribotests, a 72.80% and a 15.74% reduction in the mass loss and COF were achieved, respectively. The addition of nanoparticles was found to provide improvements of 5.31% in WSD for the AG grease and 34.49% in COF for the LG grease. A pilot test was performed following the security test UL489, achieving a reduction of 45.17% in the worn area achieved by LG grease compared to AG grease.

Catalytic behavior of colloidal dispersions of different nanocarbon additives in mineral and synthetic oil has been studied. Oxidation performance of mineral oil and synthetic oil containing detonation nanodiamonds (NDs/DNDs), detonation soot and commercial analogs have been compared with fullerenes and a conventional chemical antioxidant. Degradation characteristics of the oils were determined by total acid number (TAN) and Fourier transform infrared spectroscopy (FTIR). Both fullerenes and DNDs showed antioxidant properties in mineral oil, with DND performance depending on the method of deagglomeration. Antioxidant performance of DNDs and fullerenes in polyalphaolefin (PAO) oil is apparently less effective than in mineral oil.

AISI 4140 steel is a popular low alloy steel due to its wide applications as workpiece in the metal-mechanic industry; there are extensive research about surface modification to enhance its properties for specific applications. The focus of this study was to investigate the influence of the nature of lubricants, mineral and vegetable oils, on the tribological performance of the hardened and tempered AISI 4140 steel against alumina (Al2O3). For this purpose, friction tests were conducted in a pin on disc tribometer according to ASTM standard G 99-05, at room temperature of 25 °C and in air with about 30% relative humidity. Lubricants were selected to be commercial Holifa B22/2 oil as mineral oil and Castor Oil as bio-lubricant, with kinematic viscosity at 25 °C of 667 and 662 cSt respectively. The following conditions were settled for all the experiments: relative sliding speed of 0.05 ms-1, sliding distance of 1000 m and wear track radius of 2 mm. Friction behaviour was reported as the average kinetic friction coefficient (µK) while wear performance was evaluated as wear rate (K). In order to identify and determine wear mechanisms, worn surfaces were analyzed by optical microscopy and profilometry. It was found that, for these tribosystems, hardened and tempered AISI 4140 steel had the best friction and wear performance under lubrication with Castor Oil. The lowest µK achieved was 0.035, whereas the lowest K was 1.02x10-8 mm3/Nm. With this bio-lubricant, there were reductions in friction and wear up to 72% compared with those under mineral oil lubrication.

The role of bottom-up and top-down synthesis methods on the nanotribological response of few layer graphene (FLG) in air and various liquid environments is reported. Oxidized FLG adhesion against Si increases by a factor of 2 as compared to non-oxidized samples. Also, it is reported that the FLG center-to-edge adhesion typically exhibits a decreasing tendency. In air, a highly lubricious nanotribological response (0.03–0.04) of both bottom-up and top-down prepared samples is measured. The frictional behavior of bottom-up synthesized FLG in different liquid environments is found to depend on the absence or presence of viscous aggregates in the respective liquid. A Stribeck-like behavior is suggested for viscous synthetic lubricants, such as silicone, present as the third body in the FLG/Si tip system. Such nanoscale behavior, indicating transitions in different lubrication regimes, may be particularly important for the further understanding of liquid–graphene interfaces in novel tribological and device applications.

This paper investigates the effects of graphene nanoplatelets (GNPs) as additives in palm-oil trimethylolpropane (TMP) ester blended in polyalphaolefin. Different concentrations of GNPs that were ultrasonically homogenized in blended lubricants consist of 95 vol% polyalphaolefin and 5 vol% TMP ester. Physical properties of the nanolubricants were identified and tribological behaviors of GNP in blended lubricants were studied using standard fourball testing and surface analysis was done on the wear surfaces using scanning electron microscopy and energy-dispersive x-ray techniques. Addition of 0.05 wt% GNP in blended lubricant resulted in the lowest coefficient of friction and wear scar diameter, thus selected as the most suitable concentration of GNP in the blended lubricant. Friction and wear were reduced by 5 and 15% respectively, with the presence of 0.05 wt% GNP in the blended lubricant.

The impact of lubricants on pole-tip recession and surface morphology of hard disk drive heads in the precision lapping process was investigated with atomic force microscopy, scanning electron microscopy, and auger electron spectroscopy. In particular, the effects of deionized water, hydrocarbon oil, ethanediol, isopropanol, and ethanol lubricants were evaluated. The results reveal that proper selection of lubricant is critical for achieving optimal performance in the lapping process. A mixture of 68% hydrocarbon oil, 30% isopropanol, and 2% octadecenoic acid was found to yield the most favorable results, displaying a writer shield recession, first shield of reader recession, and surface roughness of 0.423, 0.581, and 0.242 nm, respectively.

A new approach for functionalising oxidised MWCNTs using hydroxylated imidazolium bromide via esterification reaction is reported. The bromide anion of a functionalised MWCNTs was exchanged with bis(trifluoromethanesulfonyl) imide (TFSI) through a metathesis reaction to improve its solubility in the IL medium. Composite was characterized with IR, XPS, EDX and TGA analysis, which clearly confirmed that the MWCNTs were functionalized with IL. For potential application as lubricant, the tribological properties of the IL-functionalised MWCNTs (MWCNT-IL) were also evaluated. It was confirmed that even low concentrations of MWCNT-IL composite in ILs causes a significant improvement in the anti-wear and friction properties.

Synergistic compositions of detonation nanodiamond (ND) particles in the form of 100nm aggregates in combination with molybdenum dialkyldithiophosphate were used as additives to 10W40 oils. Ring-on-disk tribological tests were performed under high load conditions using friction pairs with different hardnesses, namely normalized-normalized (“soft/soft”) and normalized-quenched (“soft/hard”) steel samples. For the “soft/hard” steel friction pair NDs provide significant reduction in both the coefficient of friction and wear as well as demonstrate polishing. For the “soft/soft” steel friction pair, however, no difference in the coefficients of friction was observed when the base oil was used with or without ND. In the test with oil containing the ND additive, the wear scar in the disk was wider, but more shallow, than in the test with pure oil. Current tests indicate that the significance of the reduction of friction and wear of the sliding surfaces in the presence of the ND additive in oil strongly depends on the hardness of the friction surfaces and most probably is connected with ND polishing effect.

Immobilization of fluorescent nanoparticles on graphene is an important step in the assembly of certain graphene-based photonic devices as well as in optical visualization of graphene and its defects. Hereby we report a viable approach to deposit diamond nanoparticles on a wide-area graphene substrate. It is demonstrated that a suitable plasma treatment leads to a selective immobilization of deposited nanodiamond on graphene with practically no agglomeration. Absence of photoemission from the individual adsorbed diamond nanoparticles suggests an energy transfer from the excited N-V centers to graphene.

The roll of lubricants in the cold-drawn process is very important to obtain a good quality on the surface of aluminum and copper wires. The viscosity of a lubricant is closely related to its ability to reduce friction. When the viscosity of a lubricant is too low, the lubricated component will have inadequate protection and will therefore be subject to excessive wear. When the viscosity of the lubricant is too high, the lubricated component will expend additional energy to complete its task. In this work, the rheology behavior of traditional lubricants for the cold drawn of Al and Cu is determined from experimental data of viscosity Vs shear rate. To evaluate the efficiency of each lubricant, the roughness surface of each wire is measured by Atomic Force Microscopy (AFM). In this way a minimum of roughness in wires corresponds to the viscosity required for each cold-drawn process. It is known that different lubricants are used for the cold drawn of Al and Cu. In this work, a new lubricant developed with the aim to be used in both process is characterized by FTIR, rheometer analysis and AFM. Results have indicated that, this new lubricant with a low viscosity that promotes a lower energy process, also decreases the roughness of Al and Cu wires compared with conventional lubricants, i.e.it has an important influence in the quality of the wires surface. This means that this new lubricant could be used during the process of both metals without making important changes, which means low operations costs and flexibility for the manufacturing plant.

In this paper, a non-destructive method is proposed for measuring the density of a verythin lubricant layer (weight and spatial) on an industrial surface. We consideredspectroscopic ellipsometry measurements on rough tinplated steel substrates protected by alubrication layer. The thickness of the coating was less than the roughness parametercharacterizing the metallic surface. As the optical properties of the substrates could notbe modelled in a conventional way due to the roughness and the complex structure of themetal, the variations of one of the ellipsometric angle (Δ) were evaluated as a functionof the lubricant film surface density. After identification of the potential outliersusing a multivariate analysis technique based on the Mahalanobis distance, we interpretedthe data using the Drude’s approximation for thin dielectric films. The values of Δlinearly decrease with the lubricant surface density, allowing us to evaluate locally thelubricant surface density and its point-to-point variations.

In the current work tribological properties of different compositions of lubricant additives based on detonation nanodiamond (DND) particles are reported. As compared to the previous findings using polyalphaolefin oil as a base oil for the additives, it is demonstrated that polymer esters are also a valuable base oil for the additive preparation. It is also demonstrated that synergistic compositions of DND with organic molybdenum provide significant improvement of the polyalphaolephin and mineral oils lubricating properties. Treatment of of DND with fluorine containing gases is an additional possibility toward reduced friction and wear of the DND-based nanolubricants.

A novel material design was developed by functionalizing a biocompatible hydrogel material with organic boundary lubricants. Polyvinyl alcohol was functionalized with varying molar ratios of 0.2, 0.5, and 1.0 moles of lauroyl chloride. Tribological and mechanical characterization was performed by means of nanofriction testing and nanoindentation to determine the influence of the hydrocarbon chains on the friction coefficient and elastic modulus of the hydrogels. It was found that fusing of the lubricant to the polymer material has a positive effect on the surface friction properties, yet an unfavorable effect on stiffness properties of the gel due to the processing method.

Lamellar liquid crystal (Lα) was formed by room temperature ionic liquid [Bmim]PF6, nonionic surfactant Tween 85, and H2O. The microstructure of this lamellar liquid crystal was investigated by small angle x-ray diffraction (SAXD) and 2H NMR (nuclear magnetic resonance). Ag nanoparticles with relatively uniform dispersion were prepared successfully in this Lα phase. The rheological and lubrication properties of the Lα phase and the Lα/Ag nanoparticle mixed system were also investigated. The results showed that the structure strength, anti-wear capacity, and lubrication properties of the Lα phase were enhanced with an increasing amount of Tween 85, but were impaired with an increasing amount of H2O. Increasing the amount of [Bmim] PF6 could also make the structural strength weaker, but the lubrication properties of the system were improved because of the inherent lubrication properties of ionic liquid. The presence of the Ag nanoparticles in the lamellar phase could also enhance the structural strength, anti-wear capacity, and lubrication properties.

In the current work we report results of tribological testing of stable colloidal dispersions of detonation nanodiamond (DND) and polytetrafluoroethylene (PTFE) in mineral oil based greases as well as in polyalphaolefin (PAO) oil. Testing has been performed on these formula-tions using ring-on-ring, shaft/bushing and four ball test techniques. The test results demon-strated significant improvements for tribological characteristics (friction coefficient, extreme pressure failure load and diameter of wear spot) for certain formulations. A strong synergistic effect when using a combination of DND/PTFE additives was observed by a sharp decrease of friction coefficient. It was also demonstrated that using DND with smaller aggregate size (10nm versus 150nm) resulted in better lubricating performance of PAO-based composition.

The evolution of carbon onion structure from spherical to polyhedral is correlated with changes in the sp3/sp2 ratio as a function of increasing synthesis temperature using electron energy loss spectroscopy, scanning electron microscopy, and high resolution electron microscopy. Results that are obtained using asymmetric f-variance versus symmetric Gaussian deconvolution of electron energy loss spectra are compared. The possibility of a separate peak at 287 eV is discussed.