Search Results (94)

Friction leads to substantial energy losses and wear in mechanical systems. This study explores the tribological potential of the high-temperature superconductor precursor Y₂BaCuO₅ (Y211), synthesized via chemical co-precipitation, as a novel additive to PAO6 base oil. A 0.3 wt.% Y211/PAO6 lubricant (CD) was formulated using ultrasonic dispersion. Tribological performance was evaluated using a custom end-face tribometer (steel-on-iron) under varying loads (100–500 N) and speeds (300–500 rpm), comparing CD to neat PAO6. The results indicate that the Y211 additive consistently reduced the coefficient of friction (COF) relative to neat PAO6, maintaining a stable value around ~0.1. However, its effectiveness was strongly load-dependent: a significant friction reduction was observed at 100 N, while the benefit diminished at higher loads (>200 N), with the COF peaking around 200 N. Rotational speed exerted minimal influence. Compared with neat PAO6, the inclusion of 0.3 wt.% Y211 resulted in a reduction in the coefficient of friction by approximately 50% under low-load conditions (100 N), with COF values decreasing from 0.1 to 0.045. Wear depth measurements also revealed a reduction of over 30%, supporting the additive’s anti-wear efficacy. Y211 demonstrates potential as a friction-reducing additive, particularly under low loads, but its high-load performance limitations warrant further optimization and mechanistic studies. This highlights a novel tribological application for Y211. The objective of this study is to evaluate the tribological effectiveness of Y₂BaCuO₅ (Y211) as a lubricant additive, investigate its load-dependent friction behavior, and explore its feasibility as a multifunctional additive leveraging its superconductive precursor structure. Full article

Background/Objectives: This study investigates the phytochemical profile, essential oil composition, and bioactivities—including antioxidant, antimicrobial, antibio-film, and anti-quorum sensing (QS) activities—of four Heracleum L. species (H. crenatifolium Boiss, H. paphlagonicum Czeczott, H. sphondylium subsp. montanum Schleich. ex Gaudin, and H. pastinacifolium subsp. incanum (Boiss. & A.Huet) P.H.Davis). Methods: Total phenolic and flavonoid contents were quantified using the Folin–Ciocalteu and aluminum chloride colorimetric methods, respectively. Essential oils were extracted by hydrodistillation and analyzed via Gas Chromatography–Flame Ionization Detector (GC–FID) and Gas Chromatography–Mass Spectrometry (GC–MS), while Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) evaluated chemical variability among the species. Antioxidant activities were assessed using DPPH and ABTS free radical scavenging assays. Antimicrobial activity was assessed using the broth microdilution method to determine Minimum Inhibitory Concentration (MIC) values, while antibiofilm activity was evaluated using an in vitro microplate-based biofilm model against Pseudomonas aeruginosa PAO1. Anti-QS activity was analyzed using a disc diffusion assay with Chromobacterium violaceum ATCC 12472 as the reporter strain. Results: It was observed that the amounts of total phenolic compounds and total flavonoids were higher in root extracts than in aerial parts extracts for the four species in this study (H. sphondylium subsp. montanum excluding phenolic content). In the analysis of essential oil, it was determined that the major component in the roots was mostly myristicin, and in the fruits it was mostly octyl acetate. Phenolic and flavonoid contents were positively correlated with antioxidant activity. Methanol and n-hexane extracts of H. pastinacifolium (aerial parts) and n-hexane extracts of H. paphlagonicum (root) exhibited notable antimicrobial activity, primarily against Gram-positive bacteria, but none of the extracts showed activity against Klebsiella pneumoniae ATCC 13383 or P. aeruginosa ATCC 27853. Among methanol extracts, H. pastinacifolium (aerial parts) exhibited the highest antibiofilm activity (73.2%), while H. paphlagonicum (aerial parts) showed the highest activity among n-hexane extracts (75.5%). All n-hexane extracts exhibited anti-QS activity, whereas the methanol extracts showed no activity. Conclusions: These findings underscore the chemical diversity and bioactive potential of Heracleum species, contributing to the chemotaxonomic understanding of the genus and supporting their potential applications in medicine and industry. To our knowledge, this is the first study that reveals the antibiofilm and anti-QS properties of these Heracleum species. Full article

The aim of this research is to analyze the thermophysical, wettability, and tribological properties of some base oils of different nature (synthetic and mineral), as well as of formulated oils, to find potential transmission oils for electrical vehicles. Regarding the thermophysical properties, viscosity, density, and viscosity index were analyzed. Surface tension and contact angle were also measured to obtain the wettability performance of tested lubricants. The highest viscosities were found for the PAO8 oil and the lowest for the G-III 3 base oil, while the highest densities were found for the formulated oils. Concerning wettability performance, the surface tensions of PAOs and G-IIIs rise gradually with an increase in viscosity, the surface tension being the greatest for G-III 6 and the lowest for G-III 3. Finally, in the tribological characterization, the lowest coefficients of friction and produced wear were found with the formulated lubricants, due to the presence of an additive package. Full article

The requirement to improve energy efficiency is constantly driving the development of high-performance and eco-friendly friction modifiers (FMs). Herein, two innovative sulfur- and phosphorus-free melamine long-chain alcohol esters (Dodec-EG-CC and Dodec-CC) are reported as novel organic friction modifiers (OFMs). Over a wide temperature range of 100 °C to 200 °C, the synthesized melamine long-chain alcohol esters, which have exceptional thermal stability, dramatically lessen wear and friction of PAO4 base oil. Dodec-EG-CC particularly reduces friction by up to 50% and wear rate by approximately 92% within this temperature range. Detailed studies of the tribological properties at elevated temperatures demonstrate that the synergistic effect of the melamine structural unit coupled with ester groups significantly enhances adsorption properties of additives on metal surfaces, improving adsorption strength and lubricating film stability. The adsorption of additives on the metal surfaces is further confirmed by surface analysis and adsorption energy calculation, which serve as a key parameter for characterizing the binding strength between molecules and surfaces. These findings demonstrate the potential of the designed triazine-based derivatives, especially Dodec-EG-CC, as OFMs in effectively reducing friction losses in motor vehicle engines. This highlights their significant potential for industrial applications in improving energy efficiency and extending engine lifespan. These in-depth studies not only provide valuable insights for the molecular structure design of OFMs, but also advances the development of sustainable lubrication technologies. Full article

The development of green lubrication requires nano-lubricants to possess more environmentally friendly fabrication modes and materials with superior tribological properties. This study investigates the tribological properties of nano-biochar in PAO6 base oil and in combination with different additives. The effect of adsorption on friction reduction and anti-wear performance is demonstrated by replacing the friction sub-materials in the four-ball friction test. Based on the comparison of wear region characterization, the incorporation of nano-biochar improves the friction reduction performance of detergent and dispersant base oils with a reduction in coefficient of friction (COF) by 16.7% and 19.0%, respectively, and produces a synergistic effect on the anti-wear performance. When nano-biochar is compounded with anti-wear agents and friction reducer, there is a synergistic effect on friction reduction performance, and COF decreases by 9.4% and 4.5% compared with anti-wear agents and friction reducer base oils, respectively. A method to analyze the friction reduction and anti-wear mechanism of nano-additives in complex lubrication system is proposed, which reveals in depth the interaction law and synergistic lubrication mechanism between NBC and additives in the friction process. Full article

This study investigates the tribological properties of Ti-6Al-4V alloy treated with single laser texturing, single thermal oxidation, and laser texturing combined with thermal oxidation in a PAO6 oil environment. The surface morphology, cross-sectional morphology, surface chemical composition, microhardness, wettability, and wear surface morphology were analyzed using a three-dimensional profiler, scanning electron microscope, electron spectrometer, X-ray diffractometer, micro-Vickers hardness tester, and optical contact angle measuring instrument. The results indicate that combining laser texturing with thermal oxidation treatment enhances groove edge hardness to approximately 1932 HV_0.2, due to the synergistic effects of laser-induced heat-affected zones and the formation of high-hardness rutile phase TiO₂. Simultaneously, the treatment effectively enhances the wettability of PAO6 oil on the surface. Furthermore, the composite-treated surface combines the oil reservoir and debris-trapping capabilities of a single laser-textured surface with the excellent load-bearing capacity of a single thermally oxidized surface. This enhancement improves the durability and reliability of the groove-type texture, leading to reduced material loss and a diminished wear rate, and significantly improving the surface wear resistance of Ti-6Al-4V alloy. Full article

Anodizing can generate porous wear-resistant layers, which can act as reservoirs for gradually releasing lubricants. Studies on the formation of zinc dialkyl dithiophosphate (ZDDP) tribofilms in non-ferrous metals are relatively rare. Furthermore, adding nanoparticles can improve wear resistance in various applications. This investigation aims to correlate several anodized surfaces using H₂SO₄ (5 or 10%wt. concentration and 45 or 60 min exposition) to tribological outputs, contributing to understanding the friction behavior of non-metallic layers. Three steps were applied on anodized Alumold 500 alloy. Firstly, the scratching test, to select the layers with higher critical loads. The greatest scratch resistance was obtained with the highest H³/E² value and thickest layer. Secondly, lubricated tests with only poly-alpha-olefin oils (PAO6) were performed in a reciprocating test rig using an alumina ball as the counterpart. From that, only the best AAO condition was selected. Finally, three more lubricant compositions were tested, as follows: adding ZDDP to PAO6, alumina nanoparticles (~100 nm) to PAO6, and ZDDP + nanoparticles. The addition of nano-alumina to the PAO6 resulted in the maintenance of COF values with only PAO6 (~0.1), when the most significant drop in the surface roughness was observed along with the tests. Full article

To address modern tribological challenges—reducing friction and wear to conserve resources while minimising environmental impact—cobalt-doped DLC (Co-DLC) coatings were developed. These nanometric multilayer coatings, designed to retain key properties such as hardness, reduced modulus, and substrate adhesion, were fabricated using non-reactive DC magnetron sputtering (DCMS). The multilayer structure was achieved by controlling the planetary substrate holder’s rotational speed. Characterisation of microscopic, chemical, structural, and mechanical properties was performed using techniques including FEI-SEM, EDS, XRD, TEM, Raman spectroscopy, scratch adhesion testing, and nanoindentation. Tribological performance was evaluated under boundary and fully flooded lubrication using PAO4 base oil and formulations with ashless, sulphur-free AW and EP additives. The coatings exhibited a granular surface morphology, columnar cross-sections, and amorphous structure. Increased dopant concentrations slightly enhanced graphitisation and significantly improved adhesion, though hardness and reduced modulus decreased. Tribological testing revealed superlubricity in several coating–oil combinations and significantly reduced wear rates with higher dopant levels and new additives. A phosphate ester additive without an amine group achieved the lowest COF values, while one with an amine group yielded minimal wear rates. These findings highlight the potential of Co-DLC coatings and tailored additives to minimise friction and wear effectively. Full article

Background/Objectives: Essential oils of Thymbra spicata subsp. spicata are known for their rich phytochemical content and bioactive properties. This study aimed to evaluate the antimicrobial, anti-biofilm and anti-quorum sensing, as well as the cytotoxic activities of T. spicata subsp. spicata essential oils (TS-EO1 and TS-EO2) obtained from two different localities in Türkiye, along with a detailed chemical composition analysis. Methods: TS-EO1 and TS-EO2 were obtained by the hydrodistillation method and analyzed using Gas Chromatography—Mass Spectrometry (GC-MS) to determine their phytochemical profiles. Antimicrobial activities were assessed against Gram-positive and Gram-negative bacteria, and fungal strains were assessed using the broth microdilution method. Anti-biofilm and anti-quorum sensing activities were evaluated using Pseudomonas aeruginosa PAO1 and Chromobacterium violaceum ATCC 12472, respectively. Cytotoxic properties were tested on four cell lines (A549, MCF-7, U87MG, and L929) using the MTT assay. Results: Both essential oil samples were rich in carvacrol (54.3% and 54.1%), followed by p-cymene and γ-terpinene. The essential oils exhibited significant antimicrobial activity, particularly against Staphylococcus aureus (6.25 mg/mL) and Candida parapsilosis (0.20 mg/mL). Sub-MIC concentrations significantly inhibited biofilm formation and quorum sensing. Both samples showed moderate cytotoxic properties against human cancer cell lines, particularly A549 (IC50: 116.3 and 134.4 μg/mL, respectively). Conclusions: This study showed that T. spicata subsp. spicata essential oils have significant antimicrobial, anti-biofilm, and anti-quorum sensing properties against various bacteria and fungi, along with moderate cytotoxic effects, indicating their medicinal and pharmaceutical potentials. This is the first study which revealed anti-biofilm and anti-quorum sensing properties of T. spicata essential oils to our knowledge. Full article

Polyalphaolefins (PAOs) are regarded as superior lubricants, but the biodegradability of the very low-viscosity PAO2/PAO4 has been ignored over a long history, despite being inherently biodegradable (PAO2/PAO4 biodegradation rate >20% by OECD guidelines). Previous studies typically concentrated on a single viscosity grade of PAO with additives, seldom engaging in comparative research efforts involving multiple low-viscosity grades of neat PAO concurrently. This study compares PAO2/PAO4 with non-biodegradable PAO6 regarding rheology and lubricating film formation. PAO2/PAO4 are Newtonian fluids with ≤10% viscosity fluctuation at high shear rates, while PAO6 shows a viscosity fluctuation of ≥15% at high shear rates. Viscosity–temperature equations are derived. An optical interference method measures lubricating film thickness. PAO2/PAO4 films are less sensitive to speed/load changes. PAO2 mainly works in boundary lubrication. Interference images show possible unique EHL characteristics of PAOs. The Hamrock–Dowson formula overestimates PAO6 film thickness at high speeds. Full article

The growing demand for sustainable lubricant solutions is driving the exploration of bio-based materials that deliver comparable performance to conventional, primarily fossil-based lubricant chemistries. This study focuses on squalane as a sustainable base oil, which can be derived from different renewable sources. A total of two squalane products were evaluated for thermal-oxidative stability and benchmarked against a polyalphaolefin, PAO 4, of the same total carbon number. Oils artificially altered in a closed reactor were sampled and subjected to conventional lubricant analyses, including infrared spectroscopy, to determine the changes due to autoxidation over time. For in-depth information, direct-infusion high-resolution mass spectrometry and gas chromatography coupled with triple quadrupole mass spectrometry were employed to identify degradation products from thermo-oxidative stress. The results revealed substantial variability in the stability of squalane products, suggesting that differences in raw materials and production processes have a major impact on their performance, including rheological properties. The degradation products of polyalphaolefin and squalane, identified through detailed mass spectrometry, were analyzed to understand their impact on conventional physicochemical properties. While polyalphaolefin predominantly generated carboxylic acids with short to medium chain lengths as degradation products, squalane oxidation produced carboxylic acids with medium to long chain lengths as well as several alcohols and ketones. Despite these differences, squalane demonstrates its potential as a non-fossil hydrocarbon base oil, as squalane products matched and even exceeded PAO 4 stability. Full article

Meyerozyma guilliermondii is an interesting oleaginous yeast with considerable potential for biotechnological applications. This yeast demonstrates the ability to utilize palm acid oil (PAO), a low-cost and renewable feedstock, as a carbon source, making it a sustainable candidate for single-cell oil production. Under optimal conditions with 4% of PAO, M. guilliermondii can accumulate lipids to approximately 45% of its cell dry weight (CDW). Notably, the expression level of PEX14, a gene associated with peroxisomal biogenesis, increases with higher PAO concentrations, coinciding with the formation of multiple small lipid bodies. These findings highlight the metabolic adaptability of M. guilliermondii and its potential for industrial lipid production using waste-derived feedstocks. Full article

Macroalgae-derived oils offer a sustainable and environmentally friendly alternative to conventional mineral oils and additives in lubricant formulation. Their favorable fatty acid profiles can contribute to mitigating the environmental impacts caused by using fossil-based products. This study evaluates the potential of Sargassum spp. oil, collected from the Mexican Caribbean, as a lubricity-enhancing additive in synthetic base oils. The impact of Sargassum spp. oil on viscosity and tribological performance was analyzed. The results indicated that Sargassum spp. oil has potential as an anti-wear additive since a formulation using 10% v/v Sargassum spp. oil in a synthetic lubricant (PAO6) resulted in a wear scar diameter value of 703.03 ± 15.56 µm, which is about 10% lower than PAO6 used as commercial synthetic control. Additionally, the formulation significantly enhanced the viscosity index, with a value of 169, which was notably higher than the control (137). The parameter of the coefficient of friction was significantly reduced from 0.1 to 0.08 (about 27%) when using the formulation with 10% v/v Sargassum spp. oil. These findings underline the potential of algae oils as additives in synthetic lubricants, promoting a transition towards greener products and reducing the environmental impact derived from conventional formulations of polyalphaolefins and esters. Full article

Lubricants are substances that reduce friction and heat dissipation between operating machine parts. The purpose of the paper is to investigate the possibility of improving the tribological properties of biodegradable vegetable oils. The objects of the research were lubricating oils produced based on selected plant oils (rapeseed, sunflower, corn, soybean) and Priolube ester oil containing nanoparticle hexagonal boron nitride (h-BN) and a dispersant. The research assesses the physicochemical properties, the wear load limit, the welding load, and the friction coefficient of the prepared oil compositions. The article compares the results with those obtained during the CB30 engine and PAO4 oil tests. The test results confirm that lubricating oils prepared in this way are characterized by promising tribological properties, are easy to prepare, and are environmentally friendly. The appropriate method of preparation has a significant impact on the quality of the obtained oils. Full article

This research thoroughly examined the tribological characteristics of polyalphaolefin (PAO4) oil, both with and without the incorporation of methyl silicone resin. The evaluation of anti-wear properties and friction reduction was conducted using a four-ball tester for friction and wear. The incorporation of methyl silicone resin into PAO4 at 25 °C significantly reduced the wear scar diameter (WSD), achieving minimum values at a concentration of 0.02 wt.%. PAO4 with 0.02 wt.% methyl silicone resin shows excellent wear resistance at different temperatures. A detailed analysis of the wear scar surfaces and wear debris was conducted using scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, 3D surface profiler and TEM. The results compellingly demonstrate that the remarkable improvement in wear resistance is predominantly due to the strategic formation of SiO₂ nanoparticles during the friction process. These SiO₂ particles not only adeptly fill the surface gaps at the friction interface but also crucially contribute to the formation of a robust tribochemical film, which is instrumental in enhancing wear performance. Full article