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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).

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

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

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

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.

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

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

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

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.

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

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

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

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 ...

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.

The aluminum sheet behavior after pulse current-assisted rolling was analyzed with hardness, abrasion, and other test methods. The hardness variations and wearability of aluminum sheets at different strain rates were evaluated. The microhardness after pulse current-assisted rolling is shown to significantly increase as compared to traditional cold rolling. The latter first decreases and then increases with the strain rate. The microhardness reaches its minimum [(79.03 ± 2.5)HV0.1] and the specific wear rate attains its maximum (0.00176 mm3/N ·m) when the strain rate ranges 65%. The pulse current-assisted rolling contributes to a lower specific wear rate of the aluminum sheet. It can also enhance the wear resistance, improve the surface lubricity, and reduce the friction coefficient of the aluminum sheet.

Energy sources are depleting at the very fast rate and the major reason behind energy depletion is the friction and wear of material. These mechanism cumulatively share 45% energy losses in mechanical components. This problem strives to find out new innovation lubrication mechanisms. In this concern, new innovation i.e. the use of nano additive based lubricant is being implemented to reduce friction and wear of materials. The scope and focus of this study is to determine the tribological behaviour of nano particles alone or in combination for minimizing the friction and wear. Nano-Aluminium Oxide (n-Al2O3), Graphene Nano Platelets (GNP) are used in this study with PAO-4 lubricant for the eutectic Al-Si alloy-chromium plated chrome steel tribopair. Various characterization techniques are used to study the wear mechanism offered during the tribological testing. The tribological test are conducted on a ball-on-disc reciprocating tribometer with 10 N load 120 m sliding distance, 2 mm stroke and 30 Hz frequency. From the results, it is reported that 0.5 wt% GNP (optimum concentration) as the nano-additive exhibit excellent tribological performance to reduce the friction and wear by 35.89% and 20.86% for the tribopair in comparison to the 1 wt% n-Al2O3 (optimum concentration) nano additive based lubricating oil. n-Al2O3 also provides good lubrication effect with optimum concentration of 1 wt% but, the results are not so effective compared to GNP based lubricant. 1 wt% n-Al2O3 + 0.5 wt% GNP i.e. Optimum hybrid Lubricant report minimum COF of 0.035 and minimum wear volume of 0.009 mm3 in comparison to other hybrid composition. Overall enhanced anti-wear and anti-friction behaviour is reported by using nano-additives based lubricants, which offers different nano lubrication mechanisms (ball bearing, mending and tribo oxide layer) to enhance the lubricity of the base lubricant.

The graphite reinforcement is a well-known material to improve wear resistance of the composite due to its inherent lubricity property. In the present work, graphite particulates of different size fractions; (3 to 10 μm, 53 to 66 μm, and 106 to 150 μm) were added in the liquid AA 7075 alloy melted in an induction furnace to fabricate the composites. It was melted and cast into mold of 45 × 45 × 120 mm3, hot forged at 490 °C at the constant strain rate of 3x10-3 s−1 to 5x10-3 s−1, and solution treated followed artificially ageing (T73 temper) at 470 °C. Carefully machined specimens were subjected to Pin-On-Disc wear test, bulk hardness measurement and SEM-EDS analysis. A threshold value of surface area to volume ratio (A/V) of graphite particulate reinforcement discussed in light of wear behavior and dislodged wear debris. A detailed worn surface analysis, transition in friction force and subsurface deformation patterns investigated to establish governing wear mechanism.

In this study, friction and wear analysis of castor oil-based biodiesel was conducted. The B0, B100, B10, B20 and B50 are the samples considered for the test. The test was performed on pin-on-disc machine at different loads 40 N and 100 N. The sliding speed of 150 rpm was considered constant and ambient temperature was taken during the analysis. It has been observed that the coefficient of friction increases with the applied load. The diesel was taken as the reference oil. The diesel (B0) shows more coefficient of friction and wear at both the loads. The minimum coefficient of friction and less wear of the surface was obtained at 100% biodiesel (B100). The increment of biodiesel blends showed better results in reducing friction, and wear of the parts during their sliding contact. Biodiesel is having better lubricity as compared to diesel and could be implemented in the diesel engine as a lubricant in near future.

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.

In this study a modest attempt has been made to develop an aluminium based hybrid composite material reinforced with silicon carbide and five different volumetric compositions of fly ash material say 0%,2.5%,5%,7.5% and 10%. The samples were prepared by using stir casting method for achieving homogeneous dispersion of SiC ceramic material and fly ash over Al359 base matrix. The five different compositions of fly ash were selected to study the impact of aluminous and silicate particles available in fly ash over the enhancement of mechanical strength and hardness properties with response to reduction of elongation percentage in specimens. The tensile, flexural and hardness tests were carried out as per ASTM standards. The results of all the five different proportions of fly ash were compared and validated. The results indicate that the addition of fly ash in lower proportion enhance good properties by initiating good lubricity between Al359 and SiC. The addition of fly ash in higher percentage resulted in gradual reduction of strength and hardness properties because of more lubricity behaviour between Al359 and SiC.

High-performance water-based drilling fluids (HPWBFs) are essential to wellbore stability in shale gas exploration and development. Laponite is a synthetic hectorite clay composed of disk-shaped nanoparticles. This paper analyzed the application potential of laponite in HPWBFs by evaluating its shale inhibition, plugging and lubrication performances. Shale inhibition performance was studied by linear swelling test and shale recovery test. Plugging performance was analyzed by nitrogen adsorption experiment and scanning electron microscope (SEM) observation. Extreme pressure lubricity test was used to evaluate the lubrication property. Experimental results show that laponite has good shale inhibition property, which is better than commonly used shale inhibitors, such as polyamine and KCl. Laponite can effectively plug shale pores. It considerably decreases the surface area and pore volume of shale, and SEM results show that it can reduce the porosity of shale and form a seamless nanofilm. Laponite is beneficial to increase lubricating property of drilling fluid by enhancing the drill pipes/wellbore interface smoothness and isolating the direct contact between wellbore and drill string. Besides, laponite can reduce the fluid loss volume. According to mechanism analysis, the good performance of laponite nanoparticles is mainly attributed to the disk-like nanostructure and the charged surfaces.

This study aims to investigate the microstructure, corrosion and tribological properties of spark plasma sintered graphene nanoplatelets (GNPs) reinforced Inconel 738 low carbon composites. The matrix and reinforcement were thoroughly milled in order to ensure homogeneity. Thereafter, the milled powders were consolidated by using spark plasma sintering. The microstructural evolution and the phases formed were examined by the using scanning electron microscopy and X-ray diffractometry techniques. The corrosion analysis was investigated in acidic and basic media, while the tribological test was conducted under dry sliding conditions at varying loads. The results show that the microhardness values were significantly influenced by varying the GNPs constituents in Inconel 738LC from 384 to 459 HV0.5, while the sintered density was influenced by the sintering parameters. The corrosion response of the sintered composites in both acidic and basic media are comparable, irrespective of the varying GNPs content in the matrix. The wear performance suggests that the addition of GNPs to IN738LC, greatly enhanced the wear resistance and reduced the friction coefficient of the sintered IN738LC-GNPs composites. The improvement is attributed to the influence of the graphene-based tribofilm that formed on the sliding contact interface, which reduced friction coefficient. Likewise, graphene has a slight potential of forming continuous tribofilms at the friction interface due to its lubricity. It is thought that the GNPs reinforcement reduced the pull-out tendency, during wear activities.

Nano-copper has proven that it has an excellent contribution to the friction-reduction, anti-wear and extreme pressure properties of lubricant, as the lubricating oil additive. However, there are few studies on the application of nano-copper in full formulated lubricating oils. The suspension stability and tribological properties of LCKD-320# lubricating oil with nano-copper of varying concentrations were investigated. The results demonstrated that the nano-copper was synthesized via the liquid-phase reduction method with the average particle size of 128 nm. The additions of Tween80 and Span80 were 2 wt% of nano-copper, respectively, which can maintain a most suitable dispersity and stability. When the addition of nano-copper was 0.3 wt%, the friction coefficient under the load of 20 N and the wear scar area (S) were decreased by 25% and 54.4%, respectively, and the maximum non-seizure loads (PB) was increased by 33% as compared with original LCKD-320# lubricating oil. Testing results showed that the LCKD-320# lubricating oil with or without nano-copper both were conformed to the national lubricant standards. The present work will extend the application of nano-copper additive and introduce a new approach to lubricity for the coal mine machinery in future technological areas.

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.

Light weight hybrid aluminium matrix composites (AMCs) were developed for brake rotor applications and their wear behaviour was compared with commercial grade material under dry-sliding wear conditions. LM27 Al-alloy was reinforced with sillimanite/rutile particles (size: 1–32 μm; loading: 0–15 wt%.). Uniform distribution of reinforcement was achieved till 15 wt% level. High nano-hardness and high thermal conductivity at particle-matrix interface indicated good interfacial-bonding. Hybrid AMCs containing 15 wt% reinforcement showed 52% decrease in wear rate over base alloy and was comparable to commercial grade material used in industries. Hybrid AMCs displayed superior thermal conductivity over commercial material. Each reinforcement played a diverse but significant role. Sillimanite improved interfacial-bonding between matrix-reinforcement whereas rutile provided increased lubricity/grain refinement of the composites.

Transition metal dichalcogenides (TMDs) are easily oxidized in the marine atmosphere environment, which results in a sharp deterioration of lubricity and limits its application. Combining two TMDs with different properties to form composite film or multilayer film is an important way to improve the performance. In this work, the MoS2/WS2 composite film and multilayer film with different microstructure characteristics were prepared by magnetron sputtering. For the MoS2/WS2 multilayer film, the regular and favorable (002) stacking plane parallel to the substrate was obtained and the compact structure was achieved by interrupting the continuity of the same component film. The multilayer interface not only significantly improved the hardness by hindering dislocation movement, but also improved the corrosion resistance by hindering the diffusion of H2O, O2, Cl− and Na+ corrosives. Consequently, the mechanical properties, the tribological properties and corrosion resistance of the MoS2/WS2 multilayer film were significantly better than that of the MoS2/WS2 composite film. The study can provide guidance for the design of high-performance and corrosion-resistant TMD films.

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.

This work aims to determine the alteration of lubricity properties of Jatropha oil (SJO) due to thermal ageing caused by approached long-term use conditions as lubricant in engines. SJO, a mineral engine oil (EMO) and a blend made of 80%vol. of EMO and 20%vol. of SJO (B20) were tested. The oils were thermally aged at 160 °C for 30 and 60h. Oil ageing was characterized by measurement of oxidation, depletion of additives, kinematic viscosity and viscosity index. Ball-on-disk tests were conducted to evaluate friction coefficients and wear rates of disks samples from engine cylinder liners by using the oils. SJO was seriously oxidized compared to EMO and B20 by ageing, exhibiting high changes of viscosity from 58.8 to 1970 cSt at 26 °C and decrease of viscosity index from 262 to 200.4. The friction coefficients of SJO were not altered remaining in low values 0.06–0.07. The viscosity increase allowed a reduction of wear rates from 0.00065 to 0.0002 mm3/m. B20 exhibited better lubricity properties than EMO; and they even were improved after ageing. Thus, SJO could be blended with mineral oils in low concentrations to reduce friction and wear while promoting safe use of a renewable product in short and long-term uses in engines.

Alcohols are reported to have superlubricity at low loads during sliding; however, their lubricity under high loads has rarely been reported. Meanwhile, the lubrication mechanism of alcohols under high loads is still not well understood. Here, we first report the lubricity of methanol under 98 N and 1450 rpm and demonstrate the formation of graphene and fullerene-like nanostructures induced by tribochemical reactions. Results show that the lubrication mechanism was mainly attributed to the friction-induced graphene under boundary lubrication condition. Besides that, the wear rate of a YG8 hard alloy ball mainly occurred at the run-in processes, and the friction-induced graphene effectively inhibited further wear after the run-in processes. The formation mechanism of graphene was well investigated, and the flash temperature rise and catalyst (WC, WO2, and WO3) were the major causes for the formation of graphene.

In order to examine the effect of sliding speeds on the elevated temperature tribological performance of atmospheric plasma-sprayed Ni-Al-Ag-MoS2 (NAMB), Ni-Al-Ag-MoS2-5 wt.% hBN (NAMB5) and Ni-Al-Ag-MoS2-10 wt.% hBN (NAMB10) composite coatings, friction and wear tests were conducted against alumina ball as a counter face using ‘a rotary ball on disk configuration’ at a constant load of 5 N and different sliding speeds 0.3, 0.5, 0.7 and 0.9 m/s from room temperature (RT) to 800 °C using a high-temperature tribometer. Both coefficient of friction and wear rate were found to decrease with increasing speed from 0.3 to 0.7 m/s with a marginal increase beyond that for all the coatings. However, coating NAMB5 exhibited better lubricity in comparison with the other coatings at all sliding speeds and temperatures. The coefficient of friction recorded for this coating decreased from 0.51 to 0.23 at a sliding speed of 0.3 m/s and from 0.48 to 0.1 at a sliding speed of 0.7 m/s as the temperature was increased from RT to 800 °C. The results indicate the existence of a synergistic action of hBN in combination with Ag and MoS2 in providing lower friction and wear, thus highlighting the potential of hBN as an effective solid lubricant to stabilize the friction in a wide range of temperatures and speeds.

Summary Viscoelasticity plays a significant role in improving the performance of the drilling fluid by manipulating its elastic properties. An appropriate value of the first normal stress difference (N1), extensional viscosity (ηe), and relaxation time (θ) enhance the cutting transportability, hole-cleaning ability, filtration loss, and lubrication behavior. However, the performance of the drilling fluid deteriorates during the drilling of high-pressure and high-temperature (HPHT) wells under acid gas and salt(s) contamination. Therefore, it is a challenging task to synthesize a thermally and rheologically stable drilling fluid, which is acid as well as salt(s) resistant, and maintain its desired properties. Although several water-soluble synthetic polymer-based drilling fluids have been used widely for the drilling of HPHT wells, most of these are limited at less than 200°C. Polyanionic cellulose (PAC) has an excellent heat-resistant stability, salt tolerance, calcium and magnesium resistant, and strong antibacterial activity, and it exhibits exceptional filtration and rheological behavior under HPHT conditions. However, using PAC beyond 200°C is limited because of the presence of the biodegradable cellulose units in it. To use the extraordinary properties of PAC, it is aimed to increase the thermal stability of PAC through appropriate modification. In this study, PAC-grafted copolymers involving acrylamide (a salt-tolerant viscosifying agent), 2-acrylamide-2-methyl-1-propane sulfonic acid (a thermally stable lubricating and fluid-loss control agent), and sodium 4-styrene sulfonate (a high-temperature deflocculant) is synthesized optimally through maximizing the thermal degradation stability of the grafted copolymer and minimizing the filtration loss as well as the coefficient of friction (CoF) of the drilling fluid simultaneously. Optimally synthesized PAC-grafted copolymers are then used to prepare water-based mud (WBM) involving American Petroleum Institute (API)-grade bentonite and alpha-glycol functionalized nano fly ash, and the tests for steady shear viscosity and viscoelasticity are performed to determine the rheological stability of mud beyond 200°C. The amplitude sweep tests for viscoelasticity are performed to determine the linear viscoelasticity range (LVR), structural stability, gel strength, and dynamic yield point (YP), whereas frequency, time, and temperature sweep tests are performed to obtain the elastic modulus (G′), viscous modulus (G″), and complex viscosity under HPHT conditions to check the stability of the drilling fluids under different holding times. Dynamic and static aging tests of the developed drilling fluids are performed at elevated temperature and pressure, and the aged muds are tested by evaluating the rheology, frictional, and filtration-loss behavior as per the API recommended procedure. The stability of the aged muds is also tested by evaluating the N1, ηe, and θ using a cone and plate rheometer. The performance of the proposed drilling fluids is also tested under acidic, sodium chloride (NaCl), and calcium chloride (CaCl2) environments at HPHT bottomhole conditions. The experimental results under HPHT conditions reveal that the performance of the mud (i.e., thermal stability, cutting transportability, hole-cleaning ability, filtration loss, and lubrication behavior) could be considerably improved by increasing the elastic properties of the drilling fluid by manipulating the molecular weight of the proposed PAC-grafted copolymer. Finally, the environmental effect of the developed muds is evaluated by finding the lethal concentration that kills 50% of the shrimp population (i.e., LC50) and the Hg and Cd contamination, and they are found to be environmentally safe.

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.

The decrease in friction is often observed in the initial period of sliding a fresh contact between two solid surfaces. This phenomenon is usually termed running-in. Here we report a running-in phe...

The heterogeneous multilayer interface of VN/Ag coatings and transition multilayer interface of VN/Ag coatings were prepared on Inconel 781 and Si(100), and the microstructures, mechanical and tribological properties were investigated from 25 to 700 °C. The results showed that the surface roughness and average grain size of VN/Ag coatings with transition multilayer interface are obviously larger than those of VN/Ag coatings with heterogeneous multilayer interface. The coatings with transition multilayer interface have higher adhesion force and hardness than the coatings with heterogeneous multilayer interface, and both coatings can effectively restrict the initiation and propagation of microcracks. Both coatings have excellent self-adaptive lubricating properties with a decrease of friction coefficient as the temperature increases, but their wear rates reveal a drastic increase. The phase composition of the worn area of both coatings was investigated, which indicates that a smooth Ag, Magneli phase (V2O5) and bimetallic oxides (Ag3VO4 and AgVO3) can be responsible to the excellent lubricity of both coatings. To sum up, the coatings with transition multilayer interface have excellent adaptive lubricating properties and can properly control the diffusion rate and release rate of the lubricating phase, indicating that they have great potential in solving the problem of friction and wear of mechanical parts.

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.

The mechanical and tribological characteristics of the VN/AlCrN multilayered coating films are investigated for cutting tools by using the arc ion plating (AIP) method with a rectilinear magnetic filtering system. The VN coating film forms vanadium oxide VxO1–x that has low friction coefficient on a surface above 500°C, whereas AlCrN coatings exhibit higher hot hardness and oxidation resistance. Therefore, the VN/AlCrN multilayer coatings are expected to demonstrate both superior lubricity and heat resistance, whose characteristics depend mostly on the combination of VN and AlCrN films. Moreover, some lower cutting force, tool wear, and tool flank temperature are obtained at high speed end milling of a prehardened stainless steel, as expected.

Fuel injector needle valve in an internal combustion engine is subjected to wear during its working over a period of time. Wear of the needle seat and needle surface is depended on the lubricity of the fuel. Wear caused to any of these surfaces will affect the performance of the engine. In the present work, the friction and wear behaviour of the needle material was studied on a reciprocating wear tester when lubricated with various blends of Karanja oil methyl ester with diesel. A high frequency reciprocating wear tester with a ball on flat geometry was used for the study. Coefficient of friction and cumulative wear depth obtained with various blends were compared. Wear scars on the ball surface and wear tracks on the flat samples were analysed. It was observed that the coefficients of friction as well as wear depth were found to be minimum when 100 % methyl ester was used

Despite many years of research, the current-carrying friction interface still strongly depends on the lubricating film between the friction pairs, because this film can reduce the probability of arc occurrence. However, this film has poor conductivity, cannot self-heal, and is prone to be greasy, which reduces the efficiency of current conduction, which seriously affects the contact status. In order to solve this problem, graphite materials with excellent lubricating properties and electrical conductivity are used to make current-carrying friction materials. Graphite and graphite-based composite materials are the most widely used current-carrying friction materials in various industries. Graphite has excellent lubricity, conductivity, and high temperature resistance to steel and many other metal materials. However, with the passage of time, due to the continuous deterioration of the application conditions and the environment, such as arc under high current density, spark phenomenon, severe mechanical wear under high load, etc., the lubricating film is destroyed, which greatly weakened the performance of protecting friction pairs. Therefore, improving the working stability of the current-carrying friction pair is the key to ensuring that the contact pair does not spark. In this review, we mainly discuss how to improve the stability of the current-carrying friction system, reduce the wear of the current-carrying friction system, and thereby extend the service life of the current-carrying friction material. At first, we discussed the latest research progress of current-carrying friction from the electrical properties, contact resistance, thermal effect, and arc of current-carrying friction materials to tribological characteristics. Secondly, the influence of contact resistance parameters and structural function parameters on the wear life of current-carrying friction pairs is discussed. The current research status of current-carrying performance and tribological performance of current-carrying friction pairs under the coupled effects of temperature field and current field is discussed. It is necessary to combine experiment, theory, and simulation to study the temperature field of the current-carrying friction pair, especially the influence of complicated conditions such as oil and dust on the friction performance of the current-carrying. Thirdly, the influence of arcing, sparking, and dynamic characteristics on the friction performance of the current-carrying friction system is reviewed. At the same time, the prediction model of current-carrying friction and wear should be studied systematically to detect current-carrying friction and wear online. Finally, it introduces in detail that new current-carrying friction materials are developing in the direction of tissue functionalization and structural composite.

Warm mix asphalt (WMA) technology can bring certain environmental and technical benefits through reducing the temperature of production, paving, and compaction of mixture asphalt. Recent studies have shown that some WMA additives are able to reduce the temperature by increasing the lubricating properties of asphalt binder-based on the tribological theory, this paper studied the mechanism of adsorbing and lubricating film of base asphalt and WMA on the surface of stone by molecular dynamics (MD) simulation method, and the effect of surfactant WMA additive on the lubrication performance of the shear friction system of “stone–asphalt–stone”. The model of base asphalt lubricating film, including saturates, aromatics, resin and asphaltene, as well as the model of warm mix asphalt lubricating film containing imidazoline-type surfactant WMA (IMDL WMA) additive molecule, were established. The shear friction system of “stone–asphalt–stone” of base asphalt and warm mix asphalt was built on the basis of an asphalt lubrication film model and representative calcite model. The results show that the addition of IMDL WMA additive can effectively improve the lubricity of asphalt, reduce the shear stress of asphalt lubricating film, and increase the stability of asphalt film. The temperature in the WMA lubricating film rises, while the adsorption energy on the stone surface decreases with the increase of shear rate, indicating that the higher the shear rate is, the more unfavorable it is for the WMA lubricating film to wrap on the stone surface. In addition, the shear stress of the WMA lubricating film decreased with increasing temperature, while the shear stress of the base asphalt lubricating film increased first and then decreased, demonstrating that the compactability of the asphalt mixture did not improve linearly with the increase of temperature.

The effect of polyvinylpyrrolidone (PVP) on the rheological properties of joint prostheses is still unclear, despite its good lubricity and biocompatibility. In the present work, PVP K30 and PVP 40-50 G solutions at different concentrations were analyzed for rheological and lubrication properties. The rheological properties of the samples were measured at a shear rate range of 0–1800 s−1 (advanced air bearing rheometer Bohlin Gemini 2 and Plate MCR 72/92 rheometer for PVP30 and PVP 40-50 G, respectively). It was found that both the viscosity and shear stress of the samples reduced with a shear rate increase. PVP 40-50 G/sterile water showed higher viscosity as compared to the PVP K30/sterile water sample at a lower shear rate. However, at a higher shear rate, the PVP K30 sample produced better results. Further numerical study results showed the pressure and molecular viscosity distributions. The inclusion of PVP improved the load caring capacity and hence, it is a promising lubrication additive for artificial joints.

The lubricating performances liquid lubricants can be enhanced by homogeneously dispersing nanoparticles as an additive and it is estimated by mechanico- dynamical test. Four-ball wear test is a standard mechanico- dynamical test used to evaluate the lubricating performances of conventional liquid lubricants by determining the lubricity properties such as wear ring width rotating top ball, load wear index of stationary lower balls and their surface texture modifications. Lubricity is the fluid property that characterizes friction and wear phenomenon in boundary lubrication regime. In this study, a methodology for estimating the lubricity properties of nanolubricants is discussed.

Lubricants play a vital role in machine life and performance, reducing friction and wear and preventing component failure. Performance-enhancing additives are a vital part of today’s modern lubricants. In response to this need, this experimental work presents the development of the new suspended nanoboric acid (nBA) additive added in engine oil that can drastically lowered friction and wear.This is a new invention of nBA additive hold in suspension and added into 5W-40 fully synthetic commercial lubricating oil. This invention is confidential and realized by Tribor ARGE Co. in Teknopark of YILDIZ Technical University in Istanbul-TURKEY.The particle size of nBA is determined with (Transmission Electron Microscopy) (TEM). Turbiscan Tower Stability Analyzer results proved that nBA particles were in suspension in commercial engine oil. Suspended nBA in engine oil is applied between ball and disk system in order to investigate their effect on friction and wear under lubricated conditions. Simulation and measurement of friction and wear were conducted using a ball on disk reciprocating tribometer UMT-3. Surface analysis was performed using 3D digital optical microscope and surface roughness, Field Emission Scanning Electron Microscope (FESEM)/X-Ray and Atomic Force Microscopy (AFM). Boron (B) from nBA is well detected, mixed with other elements of additives and protected the surface under boundary lubrication conditions. The results indicate that nBA can considerably improve the tribological performance of a ball and disk pairs under lubricated conditions. It has found that the friction coefficient is reduced with nBA suspended engine oil and protected the surface on both ball and disk mixing with other additives.

MoS2 is easily oxidized into MoO3 at elevated temperature, which leads to a sharp deterioration of lubricity and greatly limits the application. To improve the atmospheric tribology properties of MoS2 at elevated temperature, the co-deposited MoS2–W composite films are prepared by magnetron sputtering. Compared with pure MoS2, the design of three kinds of MoS2–W composite films not only maintains lower temperature-sensitivity, but also greatly improves the mechanical properties. In particular, the three MoS2–W composite films embrace good tribology performance at all test temperature, especially 100 °C, at which physical adsorption of H2O is prominently less than that of 25 °C and the oxidation is relatively slight, compared with that of the higher temperature. Individually, the MoS2-8.2%W composite film maintains the optimal tribology performance at any test temperature and becomes self-adaptive to temperature variation, which originates from the optimized structure and good mechanical properties.

The concrete mix design affects the quality and performance of the concrete. This study is based on the numerical derivation of the approximate average lubricity of the pellets (LTAavg), the establishment of a simple calculation table, and a case study comparing the ratio of traditional concrete (TC) and four-phase concrete (QBC) in terms of the slump, compressive strength, and durability. The results showed that the lubricant quantity (thickness) of the concrete could reach 15–20 cm of the slump when the proper dose of carboxylic acid superplasticizers was added, regardless of the parcels; the W/CM (quality) reached a value between 0.24 and 0.40 for any kind of concrete, while a lower water-cement ratio or a greater thickness resulted in a higher compressive strength; the strength of traditional concrete with a larger lubricant amount (48.3 μm) was still higher with a value of W/CM = 0.32, but QBC concrete with a high LQTavg value (39.0 μm) had a higher strength at 7 days, while the LQTavg value was lower (

In this study, expanded graphite and natural graphite were introduced into resin-based friction materials, and the tribological behavior of the composites was investigated. The tribo-performance of the two friction composites was evaluated using a constant speed friction tester. The results showed that the expanded graphite composite (EGC) displayed better lubricity in both the fading and the recovery processes. The wear rate of the EGC decreased by 22.43% more than that of the natural graphite composite (NGC). In the fading process, and the EGC enhanced the stability of the coefficient of friction. The recovery maintenance rate of the NGC was 4.66% higher than that of the EGC. It can be concluded that expanded graphite plays an important role in the formation of a stable contact plateau and can effectively reduce the wear.

To increase the thrust-to-weight ratio and reliability of gas turbine engines, conventional oil-lubricated bearings are desired to be replaced by fuel-lubricated bearings in fuel pumps. The...

To well play the synergy between CNF and MoS2, the hybrid of CNF/MoS2 core-shell structure were successfully prepared via a one-step hydrothermal method. And the as-prepared CNF/MoS2 hybrid showed both excellent lubricity and reinforcing effects to enhance EP composite coatings. Compared with EP and other single filler reinforced composite coatings, EP-CNF/MoS2 had better anti-friction and anti-wear properties, and the friction coefficient and wear rate were only 0.075 and 8.6 × 10−5 mm3/Nm, respectively. This was mainly attributed to the synergistic effect between CNF and uniformly loaded MoS2 as well as the good interfacial adhesion between CNF/MoS2 and EP matrix. Moreover, two feed ratios of CNF and MoS2 precursors were designed to investigate the relationship between the morphology of the synthesized heterostructure and the lubricity. And the EP-CNF/MoS2-3 possessed much better friction and wear properties than EP-CNF/MoS2-1 and EP-CNF/MoS2-2. All these suggested that CNF/MoS2 core-shell structure was a promising additive applied in tribology.

Lead-bismuth eutectic liquid metal (LBE) is the primary coolant for the advanced liquid-metal nuclear reactor, and clarification of its lubrication behavior and mechanism at elevated temperature is of importance. In this paper, a self-mated high-temperature steel sliding-pair and a pin-on-disc configuration are selected to evaluate the lubrication behaviors of LBE at 250 °C and 400 °C under argon atmosphere. It is found that LBE possesses an excellent lubricity proofed by the low friction coefficient of 0.1 and the wear rate of 10−6 mm3/Nm for the steel discs. Close inspection on the friction interfaces indicates that the worn surfaces of the steel discs are covered by a smooth tribo-film consisting of Bi, Pb7Bi3 and the related oxides.

Warm-mix asphalt (WMA) containing additives is used to decrease both the costs and harmful effects to the environment by reducing the viscosity, mixing temperature and compaction energy of asphalt without affecting its mechanical and dynamic properties. The lubricity effect is important in the densification of the mixture and must be measured during compaction (using a Superpave gyratory compactor). This work analyzes the impact of the addition of greasy diamide (DG) on the rheological-mechanical properties of dense-grade mixtures manufactured with asphalt AC-20 by examining a reference sample (HMA) and three improved samples (WMAs) with different percentages (1.5, 3.0 and 4.5%) of greasy diamide. The type of aggregate, content and type of asphalt and compaction energy were found to remain constant in the test mixtures. The rheological properties were measured according to current regulations, and the deformation was determined using a uniaxial cyclic compressive tester and a Hamburg loaded wheel. The results showed that the addition of greasy diamide to WMA improved the rheological properties while decreasing the compaction temperature and maintaining densification without significantly affecting the mechanical behavior.