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Extreme Pressure (EP) additives are commonly used in lubricants to reduce wear and prevent seizures at high temperatures and pressure. In terms of their mechanism, these build up a film on the surface with chemisorption. This film efficiently prevents metal-metal adhesion. Industrial statistics show that extreme pressure additives are mostly used in metalworking fluids, lubricating greases and engine oils. Sulfurized vegetable oils can be used as EP additives of lubricants. This type of EP additive is ashless, derived from renewable sources and has a lesser negative effect on the environment compared to those that are not derived from vegetable sources. Several technologies for the preparation of additives have been developed, of which the dark sulfurization process has been studied. Several physical and lubricating properties of the obtained additives have been investigated, based on which, it is possible to produce additives with favourable viscosity values and low copper corrosion grade. [ABSTRACT FROM AUTHOR]

At extreme deep-sea pressure, the assessment of the electroacoustic conversion performance of transducers is a major problem, particularly in the acoustic exploration of seabed sediment in 11,000-m abysses. To address this problem, an online measurement method was proposed for the electroacoustic performance under extreme pressure. The method utilized the 11,000-m transceiver with the high-frequency and narrow-beam characteristics. In the full-depth pressure profile, the transceiver signal was measured online by an extreme pressure simulation device. At different extreme pressure sites, characteristics of the transceiver signal were analyzed using the transceiver signal at atmospheric pressure as the reference. The characteristics included amplitude response characteristics, frequency response characteristics and time-frequency characteristics. The 11,000-m transceiver has verified the stability and reliability of its electro-acoustic conversion performance. It was also analysed the effect of the transducer on the calculation of seabed sediment parameters in a pressure environment. [ABSTRACT FROM AUTHOR]

The present study reports the tribological performance of a novel hybrid nano-lubricant for bronze/AISI 4340 alloy-steel tribopair. The hybrid nano-additive used in the present study helps to improve the lubricity and can sustain under extreme conditions. Initially, friction and wear properties are recorded by varying concentrations of Al2O3 (0.5, 0.8, 1.0, and 1.5 wt. %) and GNP (0.05, 0.1, 0.2, and 0.5 wt. %). Based on the results, an optimum hybrid concentration (OHC) is prepared by adding 0.8 wt. % of Al2O3 and 0.2 wt. % of GNP which resulted in 83.84% and 79.75% reductions in coefficient of friction (COF) in comparison to optimum Al2O3-based and GNP-based lubricants, respectively. However, the wear volume (WV) for OHC lubricant indicated 98.28% and 75% reduction in comparison to the above-mentioned lubricants, correspondingly. Extreme pressure (EP) tests were carried out and OHC lubricant reported improved weld point for hybrid nano additive-based lubricant. [ABSTRACT FROM AUTHOR]

The performance loss in industrial equipment due to friction and wear is one of the critical concerns among researchers. This drives the need to develop lubrication fluids that reduce friction to provide extended performance. The global sustainability movement drives the research towards novel bio-based oils to aid in lubrication. This study analyses the dispersion stability, tribological behaviour and antiwear properties of zinc oxide (ZnO), titanium dioxide (TiO2) and molybdenum di sulphide (MoS2) nanoparticles as an additive in hazelnut and sunflower oils. The viscosity index and flash point of the prepared nano lubricants were analyzed. The tribological test conducted on four ball tester resulted in a 12.6% and 35.8% reduction in coefficient of friction (COF) for 0.5% ZnO in hazelnut oil and 1% MoS2 in sunflower oil. The corresponding wear scar images were analysed. The extreme pressure (EP) test resulted that 1% MoS2 in sunflower oil exhibiting improved performance as it sustained a 1800N load. The kinematic viscosity of the 0.5% ZnO in hazelnut oil and 1% MoS2 in sunflower oil had an improvement against others. Therefore, infusion of nano additives in bio-oils offers enhanced tribological properties foreseeing sustainability in applications. [ABSTRACT FROM AUTHOR]

Ammonia is a prospective zero-carbon-emission fuel for use in large marine diesel engines. Current research focuses on several technical aspects, such as injection strategies or exhaust gas aftertreatment options, but investigations regarding the impact of ammonia on engine oil degradation are largely absent from the literature. This study provides a methodology with which to evaluate this phenomenon via artificial oil alteration. By using an admixture of various contaminations to air, such as ammonia and its partial combustion product nitrogen dioxide, their respective impacts on chemical oil degradation were assessed. Subsequently, the lubricating performance of altered oils was investigated, with a focus on corrosion properties, deposit formation, and load-bearing capability. Although the application of a stoichiometric ammonia–air mixture resulted in less pronounced thermo-oxidative degradation compared to alteration with neat air, static and dynamic deposit formation as well as corrosion properties and load-bearing capability were severely impacted by the presence of ammonia. On the contrary, nitrogen dioxide contamination resulted in higher oxidation and acidification of the oil, but altered samples performed considerably better than ammonia-altered aliquots in terms of coking tendencies, corrosivity, and load bearing. [ABSTRACT FROM AUTHOR]

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Extreme pressure (EP) and antiwear (AW) additives are necessary for boundary lubrication. However, their mechanisms and physical and chemical properties remain unclear. EP and AW additives were reviewed to fill gaps in theoretical and industrial applications. Compounds containing chlorine, sulfur, and phosphorus elements were first used in boundary lubrication because of thermal reaction with metal to form film characteristics. First, the mechanisms of traditional EP and AW additives were analyzed, the physical and chemical properties were compared, and properties affecting factors were studied. Traditional EP and AW additives are not environmentally friendly, but nanoparticle EP and AW additives are excellent substitutes. The mechanisms of nanoparticle EP and AW additives were summarized. The influence of nanoparticle structure parameters, concentration, and media polarity on properties was studied. Second, the influence law of non-polar chain length on traditional EP and AW additives was revealed. The improvement interval of traditional EP and AW additives on the performance of the base fluid was determined. The structural advantage of low crystallinity onion-like and multilayer sheet-like low wrinkle effect of nanoparticles was explained. The particle size design principle attached to the surface roughness and size-dependent melting inhibition mechanism was established. The influence of concentration and media polarity on nanoparticle properties was obtained. Finally, the research of minimum amount matching database and mathematical selection model for traditional EP and AW additives and the molecular dynamics analysis of surface-modified nanoparticles and the development of green general-purpose additives based on molecular design are prospected. [ABSTRACT FROM AUTHOR]

Copyright of Applied Chemical Industry is the property of Shaanxi Research Design Insitute of Petroleum & Chemical Industry and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present work focused on the extreme pressure characteristics of different grades of polyalphaolefins (i.e., PAO 4, PAO 6, PAO 40, and PAO 100) with LaF3 nanoparticles as an additive. The LaF3 nanoparticles were synthesized by the sol-gel method and modified with oleic acid. The synthesized nanoparticles were characterized with various analytical tools, viz. X-ray diffractometry (XRD), high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Varying doses (0.025–0.15 wt%) of synthesized nanoparticles were blended in all PAOs to prepare nanolubricants. The extreme pressure (EP) properties of nanolubricants were measured using a four-ball tester as per ASTM D2783 to find the last nonseizure load (LNSL), initial seizure load (ISL), just before weld load (JBWL), weld load (WL), and load wear index (LWI). The results revealed that the incorporation of LaF3 nanoparticles efficiently enhanced the EP properties of all PAOs. However, 0.15 wt% of additive was the optimum dose in all PAOs, demonstrating the best EP behavior; that is, the highest LWI and lowest wear scar diameter (WSD) at ISL and JBWL. Numerous characterization techniques such as scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and scan probe microscopy (SPM) were adopted to investigate the probabilistic rationale for the improvement in EP properties. [ABSTRACT FROM AUTHOR]

Purpose: The screening of lube oil performance prior to field trials is the most significant for the formulation of novel lubricants. This paper aims to investigate the efficacy of trimethylolpropane trioleate oil (TMPTO) based lubricants with different additives. Design/methodology/approach: In this endeavor, initially five lubricating blends along-with TMPTO based oil with variable additives were evaluated for their tribological performances using ASTM standards. Out of these, the top three best-performing oils were further investigated for possible physical or chemical synergies among lube oils, additives and ball surface using SEM. The molecule structures of TMPTO based lube oils were confirmed using Fourier transform infrared spectroscopy (FTIR). Findings: The wear preventive and extreme pressure characteristics of different TMPTO based samples were evaluated and compared for compatibility and synergy of additives. Morphological analysis of SEM images was used to understand the wear behavior of the worn surfaces. Practical implications: Further investigation of TMPTO oil on its oxidation stability at high temperature and pressure to make it technologically competitive and commercially viable metal-working lubricant is suggested. Originality/value: This paper highlights the tribo-effects of TMPTO to be rendered as a suitable lubricant for metal-cutting operations. The surface morphology of the worn-out surface significantly demonstrates the effect of loading conditions. [ABSTRACT FROM AUTHOR]

Four 10-undecenoic acid-based Schiff bases were synthesized by condensation of methyl 11-(2-aminoethylthio) undecanoate with various aromatic aldehydes. Synthesized compounds were characterized by spectral techniques and evaluated for their tribological and antioxidant performances in biolubricant base oil, namely epoxy 2-ethyl hexyl esters of karanja fatty acids. The tribological test results indicate that all the synthesized thioethers containing Schiff bases act as good antiwear and extreme pressure additives. A significant reduction in wear scar diameter was observed at a very low concentration (0.6 wt%), whereas, at 1 wt% concentration, weld point enhancement observed from 160 to 230 kg. Quantum chemical calculations based on density functional theory for the interactions of Schiff bases with surfaces correlated with experimental wear data. Overall, the dimethoxy-substituted phenyl ring containing Schiff base was more effective in enhancing the antiwear and extreme pressure performance of base oil, whereas dihydroxy-substituted phenyl ring containing Schiff base exhibited good antioxidant property. [ABSTRACT FROM AUTHOR]

The paper aims to study the antiwear (AW) and extreme pressure (EP) properties of avocado oil mixed with zinc dialkyl dithiophosphate (ZDDP) in concentrations of 1% to 3% by weight for lubrication purposes. The AW and EP tests are conducted as per ASTM-4172 and ASTM-2783 standards respectively. Further, the rheological behavior of avocado oil mixed with ZDDP is determined for varying shear rates of 50 – 2000 s−1. The maximum improvement in the wear properties for avocado oil is equal to 39.8% at 1 wt.%. The load wear index of pure avocado oil increases from 32.6 to 80.3 at 3 wt.% ZDDP whereas, the weld point increases to 252 kgf at 3 wt.% ZDDP. The improvement in the antiwear and extreme pressure properties are attributed to the protective film formation on the tribopairs as characterized by SEM and EDX analysis. Also, the addition of ZDDP increases the viscosity of the oil at all concentrations and maintains the Newtonian behavior of oil. [ABSTRACT FROM AUTHOR]

Purpose: The paper aims to investigate the effect of zinc dialkyldithiophosphate (ZDDP) on wear and extreme pressure (EP) capabilities of hazelnut oil. Design/methodology/approach: A four-ball tribometer is used to study the effect of ZDDP on the antiwear (AW) and EP performance of hazelnut oil as a lubricant. The AW/EP tests are carried out following ASTM D4172 and ASTM D2783 standards. The wear mechanism of steel balls is studied by scanning electron microscope (SEM). The ZDDP is added in 1Wt.%, 2Wt.% and 3Wt.% concentration, and its presence on surfaces is indicated by Energy Dispersive X-Ray Analysis (EDX). Findings: The maximum improvement in the wear properties for hazelnut oil is equal to 43.7% and 45.7% at 1Wt.% and 3Wt. % ZDDP, respectively. Also, the load wear index of hazelnut oil increases from 29 to 73.1 at 3Wt.% ZDDP. The improvement in AW and EP properties is attributed to the protective layer formation by ZDDP. Originality/value: The paper is a novel study investigating the effect of ZDDP additive in hazelnut oil. The results could prove beneficial in making the hazelnut oil a viable replacement of mineral oils. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2020-0217/ [ABSTRACT FROM AUTHOR]

Eu-doped WO3 (WO3:Eu3+) nanoparticles were prepared by Pechini method under different pH values (pH 1, 3, 5, and 7). The prepared nano-powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results showed that the average external diameter of the prepared nano-WO3:Eu3+ powders is the smallest and reaches 50 nm at pH 5. Structural transformation matrix contained different crystals of anorthic and orthorhombic structures. Eu3+ ions are located at the center of the non-inversion symmetry of WO3:Eu3+. The tribological properties of the WO3:Eu3+ as extreme pressure and wear resistance agents in water-based lubricant were investigated by a four-ball machine. The results showed that WO3:Eu3+ displays excellent load-carrying capacity, wear resistance, and friction-reducing properties in water-based lubricant, particularly in the best concentration of WO3:Eu3+ was 0.6 wt%. WSD was reduced from 0.62 to 0.35 mm and COF was decreased from 0.083 to 0.055. This was due to the formation of tribofilms with a few tens of nanometers thick, which prevented no actual metal-to-metal contact. [ABSTRACT FROM AUTHOR]

Bearings, as a key part of a vehicle transmission system, were extensively studied to improve their abrasion resistance and fatigue life. Mixtures of hard ceramic particles, namely, molybdenum disulphide (MoS2) and graphite particles (PC), were sprayed with a high-pressure inert gas onto the surface of AISI52100 bearing steel, forming the lubricant film. The morphology and phase composition of the protective layer were examined using confocal laser scanning microscopy, surface roughness tester, X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. The changes in surface microhardness were evaluated with a microhardness tester. The friction factor and anti-wear properties of the lubricant layer were assessed with an SRV-IV microvibration tester. The solid lubricant is shown to effectively reduce the friction factor. The surface modification gave a twofold increase in extreme pressure 14% reduction in the friction factor, and 20% enhancement in microhardness. This study offers a practical method to enhance the bearing surface strength for a vehicle transmission system. [ABSTRACT FROM AUTHOR]

Copyright of Scientia et Technica is the property of Scientia et Technica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A nano-copper suspension solution with an average particle diameter of about 139 nm was prepared by chemical reduction method. The surface modification of the nano-copper suspension solution using one buffer and a pair of non-ionic surfactants was carried out to study its suspension stability in 220# mining lubricant oil. And the tribological properties of the nano-copper lubricants were studied by MFT-R4000 high-speed reciprocating friction and wear tester and AW lubricant antiwear tester. The results show that when the usage of the buffer, Tween-80 and Span-80 are 233%,2% and 2% in the nano-copper suspension solution, respectively, and the amount of nano-copper modified is 0.3% in the lubricating oil, the suspension stability of the nano-copper in 220# lubricating oil is the best, and the friction coefficient is reduced by 67.07%, 15.79% and 43.40% compared with original oil under the load of 5,10 and 20 N, respectively. Meanwhile, the extreme pressure and wear resistance are improved over 20.0% and 63.9%, respectively. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the influence of polymeric viscosity improver on the tribological performance of palm kernel methyl ester (PKME). Design/methodology/approach: Tribological performances of the PKME added with the various concentration of ethylene-vinyl acetate copolymer (EVA) were evaluated using four-ball tribotester under extreme pressure condition. The morphologies of the worn surfaces were observed by using the optical microscope. Findings: The addition of polymeric viscosity improver (EVA copolymer) has produced positive results towards the tribological properties of PKME. In total, 4 per cent of EVA copolymer is found as the optimum concentration by improving the friction reducing properties and anti-wear behaviour due to the formation of film thickness between two rubbing surfaces. Originality/value: This work might contribute to the development of vegetable oils as a new source of environmental-friendly lubricant. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the anti-wear (AW) and extreme pressure (EP) performances of CuO and graphite nanoparticles as a palm oil additive. Design/methodology/approach: In this study, the AW and EP performances of CuO and graphite nanoparticles as additives in palm oil were evaluated using four ball tribotester in accordance to ASTM D4172 and ASTM D2783, respectively. The wear worn surfaces of the steel balls were analysed using high resolution microscope. Findings: The results obtained demonstrate that CuO and graphite nanoparticles improved the AW and EP performances of the palm oil up to 2.77 and 12 per cent, respectively. The graphite nanoparticles provide better AW and EP performance than that of CuO nanoparticles. Originality/value: This demonstrates the potential of CuO and graphite nanoparticles for improving AW and EP performances of palm oil base lubricant. Different morphology of nanoparticles will affect the AW and EP performances of nanolubricants. [ABSTRACT FROM AUTHOR]

A research has been done to investigate the tribological performance of palm kernel oil (PKO) with addition of different percentage of pour point depressant, PPD (5w%, 10wt%, 20wt% and 30wt%) according to ASTM D2783. The main analyses that have been done in this research are low temperature performance ability of blended PKO, coefficient of friction (COF), wear scar diameter (WSD) and surface profile. The result of the experiment has shown that for low temperature performance, PKO with 20wt%PPD (A2-20%) and 30wt%PPD (A2-30%) show great performance in withstanding lower temperature (15°C). Under extreme pressure test, it can be seen that PKO can only withstand lower load (110kg) compared to mineral oil (140 kg). The sample 10wt%PPD (A2-10%) shows good lubricity performance in terms of COF as compared to other sample. 5wt%PPD (A2-5%) and 10wt%PPD show good lubricity performance in terms of anti-wear behaviour (A2-10%) by producing the lowest WSD when compared to other samples. From overall view, PPD is considered as successful in improving low temperature performance of PKO, but in terms of lubricity performance, adding PPD will slightly reduce the lubricity performance under extreme pressure if compared to pure PKO. [ABSTRACT FROM AUTHOR]

Enzymatic synthesis of six esters of α-lipoic acid with different fatty alcohols and diols was carried out to produce novel compounds with lubricant additive properties. The synthetic route was mild and efficient with good yields. The synthesized compounds were characterized by IR, NMR, and mass spectral studies and screened for their thermal stability, antiwear (AW), extreme pressure (EP), and antioxidant (AO) properties. The tribo tests in a synthetic base fluid indicated that all the synthesized compounds act as antiwear and extreme pressure additives. All the prepared esters exhibited very good thermal stability and excellent antioxidant properties with better performance compared to commercial antioxidant BHT as determined by differential scanning calorimetry. [ABSTRACT FROM AUTHOR]

To enhance the lubricating and extreme pressure (EP) performance of base oils, two types of oil-soluble ionic liquids (ILs) with similar anion albeit dissimilar cations were synthesized. The physical properties of the prepared ILs were measured. The anticorrosion properties of ILs were assessed by conducting corrosion tests on steel discs and copper strips, which revealed the remarkable anticorrosion properties of the ILs in comparison with those of the commercial additive zinc dialkyldithiophosphate (ZDDP). The tribological properties of the two ILs as additives for poly-α-olefin-10 (PAO10) with various mass concentrations were investigated. The tribological test results indicate that these ILs as additives are capable of reducing friction and wear of sliding contacts remarkably as well as enhance the EP performance of blank PAO10. Under similar test conditions, these IL additives exhibit higher lubricating and anti-wear (AW) performances than those of ZDDP based additive package in PAO10. Subsequently, X-ray photoelectron spectroscopy (XPS) and energy dispersive spectrometer (EDS) were conducted to study the lubricating mechanism of the two ILs. The results indicate that the formation of tribochemical film plays the most crucial role in enhancing the lubricating and AW behavior of the mixture lubricants. [ABSTRACT FROM AUTHOR]

The lamellar structure of MoS2 provides very good protecting layer that can be easily sheared under the application of extreme pressures and thus enhance the antiwear performance of the chromium steel bearing aircraft grade E52100. ASTM standard 2266 uses 4-ball testing by keeping the load at 393 Newton wherein the grease is heated to 75°C and the test is conducted at a rotational speed of 1200 min-1 for 1 hour and the wear scar is measured at the end of the period. While this method is useful under fixed conditions it is not always representative of the fields where variable loads and speeds and different break in periods play a role and could change the results tremendously. The goal of this study was to examine the loads and speeds conditions with and without break in period of 30 second at the start of the test and every 7.5 minutes thereafter. This will help explain their influences on the wear properties of lithium base grease under fixed 2% MoS2 concentrations. Results indicated that wear was largely dependent on the loading condition during specific break in period at a higher rotational speed. It is believed that MoS2 greases perform better under moderate loading when break in period is used as was optimized by Design Expert analysis (DOE). MoS2 is sufficient to improve the wear characteristics at different break in period for different speeds and loads for extreme pressure applications. [ABSTRACT FROM AUTHOR]

The aim of the present study is to examine the antiwear, antifriction, and extreme pressure performance of castor oil with nano-additives by using a four-ball tester. CeO2 (~90 nm) and polytetrafluroethylene (~150 nm) nanoparticles were used as an additive in castor oil with four different concentrations in the range of 0.1-1.0% w/v. The suspension stability of the nanoparticles was improved by using sodium dodecyl sulfate as a dispersant. Different analytical tools were used to characterize the nanoparticles parameter (i.e. shape and size) as well as the worn surfaces. The additive concentration was optimized on the basis of tribological performance. The test results of antiwear and extreme pressure property have been reported on the basis of wear scar diameter and weld load, respectively. For the antiwear test, it was observed that the maximum reduction in the wear scar diameter was 37.4 and 35.3% at an optimum concentration of CeO2 and polytetrafluroethylene additive, respectively. Also, antifriction and load carrying properties of castor oil were significantly improved with the addition of nanoparticles as an additive in a small amount. The mechanism for such improvement in the tribological behavior has also been discussed. [ABSTRACT FROM AUTHOR]

Purpose The present work aims to formulate nanolubricants and improve antiwear, antifriction and extreme pressure (EP) performances of castor oil (CO) with surface-modified CuO nanoparticles as an additive in the boundary lubrication regime.Design/methodology/approach In this study, CuO nanoparticles are modified with a surfactant sodium dodecyl sulfate (SDS) by means of a chemical method. These modified nanoparticles with varying concentrations of 0.1, 0.25, 0.5 and 1.0%w/v were used to formulate the nanolubricants. The tribological properties of non-formulated and formulated CO were examined using a four-ball tester. The tribological test results were compared with paraffin oil (PO) for similar compositions.Findings The nanoparticle concentrations in base oils were optimized by wear scar diameter (WSD) and load carrying capacity during antiwear and EP tests, respectively. In the antiwear test, the maximum reductions in WSD were 28.3 and 22.2 per cent; however, the coefficient of friction was reduced by 34.6 and 17.3 per cent at optimum nanoparticle concentrations in CO and PO, respectively. A significant improvement in the weld load was observed for both nanolubricants.Originality/value This work indicates that nanoparticle-based CO in industrial applications provides on par or better results than mineral oil. Also, it has a negligible hazardous impact on our eco-system. [ABSTRACT FROM AUTHOR]

Copyright of Petroleum - Gas University of Ploiesti Bulletin, Technical Series is the property of Petroleum - Gas University of Ploiesti and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Dyna is the property of Universidad Nacional de Colombia, Medellin, Facultad de Minas and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the present work, calcium-copper-titanate (≈85 nm) and cerium oxide (≈90 nm) nanoparticles were blended in paraffin oil (PO) as an additive by varying the concentration from 0.1 to 1.0% w/v, and tribo-performance was evaluated with four-ball tester. The concentration 0.25% w/v of the nanoparticles in PO was found to be optimum in antiwear and antifriction property tests for both types of nanolubricants. At this particular concentration, the maximum reductions in the wear scar diameter were 38.4 and 26.1% for calciumcopper- titanate and cerium oxide-based nanolubricants, respectively. Also, the mean coefficient of friction was reduced by 17.3 and 29.6% at this optimum concentration for both types of lubricants. For extreme-pressure test, the loadcarrying capacity of the nanolubricants was improved from 126 to 160 kgf as compared with base PO. The worn surfaces were examined with scanning electron microscope, energy-dispersive spectroscopy, and atomic force microscope to study the physical phenomena that occurred during the sliding. [ABSTRACT FROM AUTHOR]

This paper investigates the tribological characteristics of modified jojoba oil (MJO) as a base stoke for SAE20W40 mineral oil (LO). In addition, a graphene nanoparticle was also added as an additive in MJO and studied for its performance. MJO was obtained from a two-stage transesterification process: acid esterification and base esterification. Six samples were formulated with the partial replacement of modified jojoba oil as 0, 10, 20, 30, 40 and 50 % by volume to the SAE20W40 mineral oil. Tribological tests were conducted on a four ball tribometer test rig under extreme pressure and anti-wear conditions with the formulated blends. Subsequently, 0.075 wt% of graphene nano additive was added in the above mentioned oil ratios and investigated once again in a four ball tester. Surface analysis was carried out, using scanning electron microscope (SEM). The experimental results showed that the blend of 20 % jojoba oil exhibited a lower wear scar diameter than other blends at extreme load conditions. An addition of 0.075 wt% of graphene nano-additive to the formulated blends also enhanced its lubrication properties. The surface characteristic study revealed that the addition of nano additives witnessed lesser wear scars with 10 and 20 % of jojoba blends. Among the blends, 20 % of jojoba oil was considered as an acceptable blend to enhance the mineral properties in comparison with SAE20W40 mineral oil. [ABSTRACT FROM AUTHOR]

Purpose Thiadiazole compounds and their derivatives have carrying capacity and good lubricating properties. However, their poor oil-solubility limited their wide usage in lubricating oil. The study aims to develop thiadiazole lubricant additives with better oil-solubility. When the hindered phenol antioxidation functional group and alkyl-chain are introduced to thiadiazole, the resulting product could have better oil-solubility and excellent antioxidation resistance, anti-wear and corrosion resistance in the lubricating oil.Design/methodology/approach One kind of thiadiazole lubricant additive, for the first time, has been synthesized from 2,5-dimercapto-1,3,4-thiadiazole. Its tribological performance has also been evaluated by four-ball test. And, its oxidation resistance has been estimated by rotating pressure vessel oxidation test and pressurized differential scanning calorimetry. The anticorrosion performance of such an additive has been studied by GB/T 5096 standard method test.Findings The synthesized thiadiazole additive has excellent anti-oxidation capability, good anti-wear and extreme pressure properties and good anticorrosion performance, in comparison with zinc dialkyl dithiophosphate (ZDDP). In base oils, the comprehensive performance of thiadiazole additive is comparable to ZDDP. Mechanistic studies indicate that the S and N active elements were involved in the formation of a boundary film. This may account for the formation of a composite membrane on the metal surface and thus for the tribological performance of such thiadiazole additives.Originality/value The thiadiazole derivatives, which are ashless and have environmentally friendly features, are a potential alternative to ZDDP. Because of the film formed on the friction surface, thiadiazole compounds may serve as an excellent anti-wear additive and are expected to reduce friction and wear between metals. [ABSTRACT FROM AUTHOR]

A four-ball tester was used to evaluate the tribological performances of bismuth naphthenate (BiNap), sulfurized isobutene (VSB), and their combinations. The results show that the antiwear properties of BiNap and VSB are not very visible, but they possess good extreme pressure (EP) properties, particularly sulfur containing bismuth additives. Synergistic EP properties of BiNap with various sulfur-containing additives were investigated. The results indicate that BiNap exhibits good EP synergism with sulfur-containing additives. The surface analytical tools, such as X-ray photoelectron spectrometer (XPS) scanning electron microscope (SEM) and energy dispersive X-ray (EDX), were used to investigate the topography, composition contents, and depth profile of some typical elements on the rubbing surface. Smooth topography of wear scar further confirms that the additive showed good EP capacities, and XPS and EDX analyzes indicate that tribochemical mixed protective films composed of bismuth, bismuth oxides, sulfides, and sulfates are formed on the rubbing surface, which improves the tribological properties of lubricants. In particular, a large number of bismuth atoms and bismuth sulfides play an important role in improving the EP properties of oils. [ABSTRACT FROM AUTHOR]

The use of fluorinated mix catalyst (titanium fluoride: TiF3 + iron fluoride: FeF3) with polytetrafluoroethylene: PTFE in engine oil is increasingly a strategy to improve fuel economy and component durability to simultaneously provide low friction and excellent wear protection. The influence of these additives shows promising results during load bearing capacity testing and long-term durability experiments. This paper addresses the enhancement of friction and wear performances of 0.1% and 0.05% phosphorus plain zinc dialkyl dithiophosphate (ZDDP) oil and fully formulated engine oil when heated to 100°C for specific time under thermal and tribological conditions for moderate pressure loading (1.9 GPa Hertzian pressure or 180 N) which simulate the cold start of a car under 700 rpm rotational speed or the valve trains loading where most of the ZDDP are applied. Tests were performed in a ball on cylinder tribometer under boundary lubrication conditions. Surface analyses were carried out using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results showed that the anti-wear additives (2 wt. % PTFE + 0.5 wt. % FeF3 + .5 wt. % TiF3) provided excellent wear protection to 0.1% phosphorus plain and fully formulated oil when cylinder is immersed in the desired lubricant and heated for a predetermined time but performed poorly in 0.05% phosphorus fully formulated oil under the same conditions. The transform of anti-wear coated material to the worn surfaces, which was a function of the anti-wear performance of additives, was shown to have an influence on friction performance. The wear reducing effect, which was observed in fluorinated additives tribological tests, indicated a positive contribution and good tribofilm formations. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Zinc Dialkyl Dithiophosphate (ZDDP) is a well-known multifunctional additive for soap based lubricating greases. Polymers are being studied for their performance as lubricating grease thickeners and rheology modifiers. In this work the tribological study of ZDDP was carried out in polypropylene (PP), maleated polypropylene (mPP) and linear low density polyethylene (PE) thickened lubricating greases. Performance of lithium grease was taken as a reference. The tribological properties were evaluated using a four ball tester for EP properties and Optimol SRV-III machine for coefficient of friction. The mechanism of action of ZDDP in polymer greases was established through analysis of the worn surface of steel balls with scanning electron microscope (SEM) and energy dispersive x-ray spectroscopy (EDAX). The results show that the performance of ZDDP depends on the thickener system. The antiwear and EP property exhibited by ZDDP varies from polymer to polymer. Poor performance was observed with PP type thickener whereas performance in PE and lithium grease was comparable. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Purpose – This study aims to examine the effect of the antiwear resistance of plain zinc-dialkyldithiophosphate (ZDDP) oil in the presence of Titanium-fluoride/iron-fluoride/polytetrafluoroethylene (TiF3/FeF3/PTFE) in the time to tribofilm breakdown and extent of wear under extreme boundary lubrication using a contact load of 317 Newton and a rotational speed of 700 rpm to simulate the cold start of a car engine. The mechanism of tribofilm formation and breakdown was followed carefully by monitoring the friction coefficient for different surface roughnesses over the duration of several reproducible tests that were performed in a ball on cylinder tribometer. Design/methodology/approach – The heating time of the cylinder dipped in the specified lubricant blend then set for one minute before testing and the break in period of 2 minutes to cool the contacting metal to metal surfaces during tribological testing played important roles in minimizing friction and wear, and are directly proportional to the durability and time for breakdown of the tribofilm. This article addresses the improvement of water drop contact angles for different surfaces during heat treatment and the tribological enhancement of antiwear additives when optimum concentration of fluorinated catalysts and PTFE is used in connection with reduced surface roughness and break in period. Findings – Design of Experiment software, scanning electron microscopy, energy dispersive spectroscopy and nanoindentation were used in this study to evaluate the antiwear resistance films when using 0.05 per cent phosphorus ZDDP plain oil with 0.5 weight per cent TiF3 + 0.5 weight per cent FeF3 + 2 weight per cent PTFE and when applying 2 minutes break in time to cool down the contacting bodies when temperature rises. Results indicated that the coated film on the thermally treated surfaces that is reflected as white patches on the SEM images is a function of the antiwear additives contribution; it is also shown to have positive influence on the friction and wear performances during tribological testing. Originality/value – This research involved the study of lubricant and surface interactions with antiwear additives under boundary lubrication and extreme pressure loading. Several researchers studied these effects and submitted articles to the journal. This is the first time that a break in period was used with surface conditions to simulate car stops in heavy traffic conditions. [ABSTRACT FROM AUTHOR]

In this study an extreme pressure and anti-corrosion additive package for gear oils has been created. In this context three different organic molecules were synthesized. Methylene-bis (dibutyldithiocarbamate), Sulfured oleic acid and o,o-Dialkyldithio Phosphate. Mass spectrums and Elemental analyses were carried out for these three molecules. For each molecule 4-ball weld points (WP), 4-ball Wear Scar Diameter (WSD), Copper corrosion (CC) and salt spray tests (SS) were carried out. Antioxidant properties of synthesized molecules were determined. According to the test results eight different additive packages were prepared and WP, WSD, CC and SS tests were applied to each package to determine a suitable package content. The highest yield was obtained in the five and six additive package with 250, 300 kg weld point and 0.41, 0.53 mm scar diameter respectively. For all additive packages the extreme pressure and corrosion resistance properties of gear oil increase by increasing the percentage of Methylene-bis (dibutyldithiocarbamate). o,o-Dialkyldithio Phosphate showed the highest antioxidant activity and it has been obtained bets corrosion protection with Sulfured oleic acid. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results for the extreme pressure characteristics of a palm oil-based trimethylolpropane (TMP) ester blended with paraffin oil obtained using a four-ball machine. The load and speed of the sample were set between 20–120 kg and 1770 rpm, respectively. TMP ester produced from palm oil is biodegradable and has high lubricity properties, such as a higher flash point temperature and viscosity index. It has an affinity to surface asperities, which reduces wear between sliding contacts. Based on the calculation, it was found that majority of the oils in boundary regime and mixed elastrohydrodynamic regime. For the same contact load, the film thickness with TMP100 is 70% thicker than that with paraffin oil. In addition to that, test results revealed that (1) for all the used lubrication oils, TMP ester blended with paraffin provide better surface protection compared to paraffin oil. (2) Even though, TMP100 has the highest film thickness, at low load the wear is higher. Surface morphology test was conducted using scanning electron microscope and surface roughness tester. It was found that severe corrosive wear occurred at TMP100 which is probably due to the high oxygen content compared to other lubricant. [ABSTRACT FROM PUBLISHER]

Purpose – The purpose of this paper is to study the antirust, tribological performance and anti-wear (AW) mechanism of the of soybean lecithin (SL) as a kind of multifunctional lubricant additive. Design/methodology/approach – As a kind of multifunctional lubricant additive, the antirust performance of SL was tested according to ASTM D 665, and meanwhile, its tribological performances were also evaluated by Optimol SRV-I oscillating reciprocating friction and wear tester and four ball tester. The worn steel surfaces were investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). Findings – The results showed that the SL exhibited excellent antirust properties in different base stock, and could effectively improve the AW and extreme pressure (EP) performances. The results of SEM and XPS indicated that a protective film was formed between steel-steel friction pair during the tribological test. Originality/value – This paper first investigated the antirust properties and the tribological mechanism of the SL as a kind of multifunctional lubricant additive, which can be very useful and will promote the application of SL in lubricant industry. [ABSTRACT FROM AUTHOR]

Stepped spillways have been increasingly used to handle flood releases from large dams associated with hydropower plants, and it is important to evaluate the fluctuating pressure field on the steps. Hydraulic model investigations were conducted on three 53° (1V:0.75H) sloping and relatively large-stepped chutes to characterize the mean, fluctuating, and extreme pressures acting on the most critical regions of the step faces, near their outer edges. The pressure development along the chutes is presented, generally indicating an increase of the modulus of pressure coefficients up to the vicinity of the point of inception of air entrainment, and a decrease further downstream. The extreme pressure coefficients along the spillway are fitted by an empirical formula, and the critical conditions potentially leading to cavitation on prototypes are calculated. The correlation between the cavitation index and the friction factor is also applied for predicting the onset of cavitation on prototypes, and the results are compared with the pressure data-based method. Generally, the results obtained from those methods yield typical values for the cavitation index in the vicinity of the point of inception, varying approximately from 0.8 to 0.6, respectively. In light of these results, maximum unit discharges of about 15–20 m2/s are considered advisable on 53° sloping large-stepped spillways without artificial aeration, for step heights ranging from 0.6 to 1.2 m. For much higher unit discharges, a considerable reach of the spillway may potentially be prone to the risk of cavitation damage. [ABSTRACT FROM AUTHOR]

The lubrication mechanisms of water-based fluids are not yet well understood, especially when extreme load conditions are applied. The example of lamellar crystallite particles in water, provided by an emulsion-like technology, is described in this paper. It is shown, for the first time, that the presence of such nanostructures in the sliding interface can provide extreme-pressure lubrication. This water-based lubricant is particularly efficient when one of the two solid surfaces is made of brass. In this case, a multilayer is created in the contact. It is formed by a brass layer transferred to the counter face, the brass surface itself and a lamellar film adherent to the former layers. This lamellar system is able to sustain pressures up to a few GPa and to maintain a low friction coefficient. [ABSTRACT FROM AUTHOR]

Tribological properties of lithium potassium titanate (PT), molybdenum disulphide, and tungsten disulphide-dispersed mineral oil (MO) were investigated. The sample containing 2 wt.% WS2 exhibited the lowest coefficient of friction. However, the wear scar diameters of the additivated samples were very narrow. Extreme pressure properties of mineral oil were enhanced with the addition of additives. The rolling contact fatigue results exhibited better fatigue life of the balls in MoS2 and PT-dispersed MO. Surface characterization of the balls indicated more pitting on the balls of the MO and WS2-dispersed MO as compared to MoS2 and PT, indicating a stable film in the case of MoS2 and PT, which was confirmed by the presence of additives on ball surfaces by Raman spectrograph. The results of extended rolling contact fatigue tests proved that PT-added mineral oil provided the highest life cycles of the tested balls, followed by MoS2 and WS2-added mineral oil; thus, indicating PT as a plausible alternative to MoS2 and WS2. [ABSTRACT FROM AUTHOR]

Pressure fluctuations are a key issue in hydraulic engineering. However, despite the large number of studies on the topic, their role in spatial hydraulic jumps is not yet fully understood. The results herein shed light on the formation of eddies and the derived pressure fluctuations in stilling basins with different expansion ratios. Laboratory tests are conducted in a horizontal rectangular flume with 0.5 m width and 10 m length. The range of approaching Froude numbers spans from 6.4 to 12.5 and the channel expansion ratios are 0.4, 0.6, 0.8, and 1. The effects of approaching flow conditions and expansion ratios are thoroughly analyzed, focusing on the dimensionless standard deviation of pressure fluctuations and extreme pressure fluctuations. The results reveal that these variables show a clear dependence on the Froude number and the distance to the hydraulic jump toe. The maximum values of extreme pressure fluctuations occur in the range 0.609 < X < 3.385 , where X is dimensionless distance from the toe of the hydraulic jump, which makes it highly advisable to reinforce the bed of stilling basins within this range. [ABSTRACT FROM AUTHOR]

Pressure fluctuations beneath hydraulic jumps potentially endanger the stability of stilling basins. This paper deals with the mathematical modeling of the results of laboratory-scale experiments to estimate the extreme pressures. Experiments were carried out on a smooth stilling basin underneath free hydraulic jumps downstream of an Ogee spillway. From the probability distribution of measured instantaneous pressures, pressures with different probabilities could be determined. It was verified that maximum pressure fluctuations, and the negative pressures, are located at the positions near the spillway toe. Also, minimum pressure fluctuations are located at the downstream of hydraulic jumps. It was possible to assess the cumulative curves of pressure data related to the characteristic points along the basin, and different Froude numbers. To benchmark the results, the dimensionless forms of statistical parameters include mean pressures (P*m), the standard deviations of pressure fluctuations (σ*X), pressures with different non-exceedance probabilities (P*k%), and the statistical coefficient of the probability distribution (Nk%) were assessed. It was found that an existing method can be used to interpret the present data, and pressure distribution in similar conditions, by using a new second-order fractional relationships for σ*X, and Nk%. The values of the Nk% coefficient indicated a single mean value for each probability. [ABSTRACT FROM AUTHOR]

A kind of novel compound containing S and Mo elements was synthesized. Its chemical structure was characterized by elemental analysis, IR and NMR. Its anti-wear property and the load-carrying capacity, as an extreme pressure (EP) additive of lubricating oil, were investigated using a four-ball tester. The experimental results show that the additive exhibits a superior anti-wear property and a high load-carrying capacity. The presence of other additives does not interfere with the anti-wear property of the extreme pressure additive. The influences of load and temperature on the property of the additive were examined. The possible mechanism was investigated by means of surface analysis of the tested steel ball specimen, using XPS. The lubrication films formed on the rubbing surface are mainly composed of MoS2, MoO3 and MoO2. [ABSTRACT FROM AUTHOR]