Viscosity and tribology of copper oxide nanofluids

Nanofluids, a term proposed by Choi in 1995 [1], are composites consisting of solid nanoparticles with sizes varying generally from 1 to 100 nm dispersed in a liquid. Numerous nanoparticles used as oil additives have been investigated in recent years [2-7]. Results show that they deposit on the rubbing surface and improve the tribological properties of the base oil, displaying good friction and wear reduction characteristics even at concentrations below 2%wt. Although the viscosity of the nanofluids is a property of crucial importance for film forming, and hence friction and wear reduction, which are characteristic of lubricants, only Hwang et al. [8] have studied thermal characteristics, kinematic viscosity and tribological properties of nanofluids simultaneously. In this paper, we present measurements of dynamic viscosity of nanofluids formed by copper oxide nanoparticles dispersed in a polyalphaolefin, for temperatures and concentrations varying from 20 to 60ºC and 0.5 to 2% wt., respectively. Dependence of the nanofluid viscosity to the solid fraction and temperature was compared with existing models and its influence on lubrication was also analysed

Corrosion activity and solubility in polar oils of three bis(trifluoromethylsulfonyl) imide/bis(trifluoromethylsulfonyl) amide ([NTF2]) anion-based ionic liquids.

The corrosion behaviour and solubility of three bis(trifluoromethylsulfonyl)amide1 ([NTf2]) anion-based ionic liquids: 1-dodecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C12MIM][NTf2]), tributylmethylammonium bis(trifluoromethylsulfonyl)amide ([N4441][NTf2]), and methyltrioctylammonium bis(trifluoromethylsulfonyl)amide ([N1888][NTf2]), as a component in a mixture with different base oils were analysed. Six polar oils suitable for use in lubrication were utilized as base oil. Solubility tests were performed by using turbidimetry, and corrosion was checked at 4 v/v% by examining the roughness and chemical composition of the surface after 21 days. The results showed that long carbon chains in the cation improve the solubility greatly in diesters and slightly in polyolesters. Corrosion was not detected at this concentration

Wetting Properties of Seven Phosphonium Cation-Based Ionic Liquids

This paper studies the wetting properties of seven phosphonium cation-based ionic liquids: trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate [P66614][(iC8)2PO2], trihexyltetradecylphosphonium bis(2-ethylhexyl)phosphate [P66614][BEHP], trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl) imide [P66614][NTf2], tributyltetradecylphosphonium dodecylbenzenesulfonate [P44414][DBS], tributylethylphosphonium diethylphosphate [P4442][DEP], trihexyltetradecylphosphonium dicyanamide [P66614][DCA], and trihexyltetradecylphosphonium chloride [P66614][Cl]. The surface tension was analyzed using the Gibbs free energy in a temperature range of 293-353 K, obtaining the expected linear decrease with temperature rise. The contact angle was measured on four different surfaces (AISI 52100 steel, CrN, TiN, and ZrN) and all liquids with high surface tensions interacting with hydrophobic systems displayed high contact angles as expected. The polarity fraction (PF) and the spreading parameter (SP) were estimated to complete and improve the wetting characterization of these ionic liquids, finding TiN-[P66614][BEHP] and TiN-[P66614][(iC8)2PO2] as the most favorable surface-ionic liquid combinations from a wetting point of view

Tribological behavior of oils additised with a phosphonium-derived ionic liquid compared to a commercial oil

Purpose: The purpose of this paper is to study the antifriction, antiwear and tribolayer formation properties of the trihexyltetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate ionic liquid (IL) as additive at 1 wt.% in two base oils and their mixtures, comparing the results with those of a commercial oil. Design/methodology/approach: The mixture of the base oils used in the formulation of the commercial oil SAE 0W20 plus the IL was tested under rolling/sliding and reciprocating conditions to determine the so-called Stribeck curve, the tribolayer formation and the antifriction and antiwear behaviors. Findings: The use of this IL as additive in these oils does not change their viscosity; improves the antifriction and antiwear properties of the base oils, making equal or outperforming these properties of the SAE 0W20; and the thickness and formation rate of the tribolayer resulting from the IL-surface interaction is highly dependent on the type of base oil and influence on the friction and wear results. Originality/value: The use of this IL allows to replace partial or totally commercial antifriction and antiwear additives. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2020-0179/

Physicochemical, traction and tribofilm formation properties of three octanoate-, laurate- and palmitate-anion based ionic liquids

Three new ionic liquids with different anions and the same cation were synthesized from fatty acids through a metathesis reaction.All the ionic liquidswere identified viaNMRand FTIR and several properties (density, viscosity, thermal, and environmental) were measured. Traction tests were performed under different entrainment speeds (10–2000 mm/s), at slide-roll ratio (SRR) of 50% and 30 N-load, and at different temperatures (40, 60, 80 and 100 °C) using a mini-traction machine (MTM). Tribofilm formation tests were also made in the MTM at 50 N-load, 150 mm/s of entrainment speed, at SRR of 50% and temperature of 100 °C, for 60 min. This work showed that the alkyl chain length in the anion affects properties such as viscosity, toxicity, biodegradability and lubrication. Viscosity decreased with increasing alkyl chain length but only below 60 °C, at higher temperatures the viscosity values of the ionic liquids converge. The toxicity increases with the alkyl chain length; whereas, biodegradability shows the opposite behavior. These novel ionic liquids are much better from both toxicity and biodegradability points of view than the [N8881][TFSI] ionic liquid, which contains the same cation and anion not coming from fatty acids. The ionic liquids at low temperature (40 °C) performed under elastohydrodynamic lubrication and changed to mixed lubrication at higher temperatures and decreasing speeds, according to the alkyl chain length of each anion. All ionic liquids adsorbed on the steel surfaces, and the tribofilm thickness and the kinetics of formation were different

Influence of environmental conditions and oxidation on the coefficient of friction using microalloyed rail steels

© IMechE 2020. In railway systems, certain atmospheric conditions – mainly related to temperature and relative humidity – lead to the creation of iron oxides which can affect the coefficient of friction between the wheel and the rail. This can result in increased wear of the rail, reducing its service life and thus increasing replacement costs. Pin-on-disc tests were conducted in a climate chamber to study the influence of environmental conditions and iron oxides on the coefficient of friction. The iron oxides generated on the surface of specimens extracted from microalloyed rail steel during wear tests were analysed using X-ray diffraction. The results show that hematite (α-Fe2O3) is the predominant iron oxide among all the oxides generated on the worn surfaces. It was further noted that the oxide layer resulting from the rise in both temperature and relative humidity does not significantly affect the average coefficient of friction for each steel samples tested. High relative humidity combined with high temperature leads to the formation of α-Fe2O3, which tends to increase the coefficient of friction. However, a boundary lubrication effect is observed at higher relative humidity due to a condensed water film, which reduces the coefficient of friction and counteracts the increase of the coefficient of friction expected due to the presence of hematite

Lubrication performance of an ammonium cation-based ionic liquid used as an additive in a polar oil.

This paper studies the tribological behavior of the ionic liquid methyltrioctylammonium bis(trifluoromethylsulfonyl)imide ([N 1888 ][NTf 2 ]) as additive at different concentrations (1.25, 2.50, 3.75 and 5.00 wt%) in a polar base oil (diester). A tribometer using a ball-on-disk reciprocating configuration under fully flooded lubrication was used at a frequency of 15 Hz, at three different loads (40, 80 and 120 N), stroke length of 4 mm, and duration of 45 min. Worn surface on the disk was studied by confocal microscopy, SEM and XPS. Main results showed similar coefficient of friction for all lubricant samples; but different wear results were found at different loads, probably related with the chemical states found for fluorine on the worn surface and the temperature-dependent adsorption-desorption processes

HÁBITOS ALIMENTARIOS DE LAS MUJERES EN RELACIÓN CON EL NIVEL DE CONOCIMIENTOS SOBRE EL CLIMATERIO

Objectives: Knowing the behaviors related to food and toxic habits of women aged 30-60 years in the health area of Vigo.Determine whether menopausal women have healthier behaviors than non menopausal ones. Identify whether any of the socio-demographic variables has an influence on feeding habits or toxic behaviors.Determine whether women with high-very high knowledge have proper habits.Methods: Comparative, observational cross study made of 425 women between 30 and 60 years of age. We used a booklet with personally answered questionnaires, one about menopause and the other about feeding behaviors during the climacteric stage, which includes socio-demographic variables. Data analysis was carried out using SPSS 14.0.Results: A result of 74.3% of the women in the sample has a high/very high level of knowledge but behaviors that do not correlate with this.Conclusions: Women know what they must do to maintain a healthy life, but the majority does not put this into practice. We think it is necessary to introduce in health centers a program about the climacteric stage, coordinated by nurses and midwives and focused on applying to daily life the knowledge that women already have, with the aim of helping them to achieve a better quality of life.This study is part of a wider research on “Knowledge and behaviors related to climacteric stage in women between 30 and 60 years of age in the health area of Vigo sponsored by the “Fondo de Investigaciones Sanitarias” (Spanish Health Research Fund) in 2007Objetivos: Conocer los comportamientos relacionados con la alimentación y hábitos tóxicos de las mujeres de edad comprendida entre 30-60 años del área sanitaria de Vigo.Averiguar si las mujeres menopáusicas tienen comportamientos más saludables que las no menopáusicas.Identificar si alguna de las variables sociodemográficas influye en los comportamientos sobre la alimentación y hábitos tóxicos. Determinar si las mujeres con conocimientos altos-muy altos tienen comportamientos adecuadosMétodos: Estudio comparativo, observacional, transversal, realizado a 425 mujeres de 30-60 años. Se utilizó un cuadernillo con dos cuestionarios autocumplimentados, uno de conocimientos sobre la menopausia y otro sobre los comportamientos relacionados con la alimentación en la etapa del climaterio, incluidas las variables sociodemográficas. El análisis de los datos se realizó mediante SPSS 14.0.Resultados: Las mujeres de nuestra muestra tienen conocimientos altos-muy altos en un 74,3% y unos comportamientos que no se correlacionan con el nivel de conocimientos.Conclusiones: Las mujeres conocen qué es lo que deben realizar para mantener una vida saludable, pero a la hora de ponerlo en práctica no lo hacen mayoritariamente. Consideramos necesaria la implantación en los Centros de Salud, de un programa coordinado por el equipo deEnfermería Global Nº 20 Octubre 2010 Página 2salud, dirigido a aplicar los conocimientos que han demostrado poseer las mujeres a los comportamientos diarios, con el objetivo de alcanzar una mayor calidad de vida. Este estudio forma parte de una investigación más amplia realizada sobre los “Conocimientos y comportamientos relacionados con el climaterio de las mujeres de 30-60 años del Área Sanitaria de Vigo” becado por el Fondo de Investigaciones Sanitarias (2007)

Tribological performance of three fatty acid anion-based ionic liquids (FAILs) used as lubricant additive

This paper studies the tribological behavior of three fatty acid anion-based ionic liquids: methyltrioctylammonium octanoate ([N8881][C8:0]), methyltrioctylammonium laurate ([N8881][C12:0]) and methyltrioctylammonium palmitate ([N8881][C16:0]) used as additive at 0.5, 1 and 2 wt% in an ester base oil. The tribological experiments were performed in two different tribometers: a Bruker UMT-3 using a reciprocating “ball-on-disc” configuration for pure sliding tests and a Mini Traction Machine (MTM) for rolling/sliding tests. After sliding tests, the wear scar was analyzed by scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS). Sliding tests results showed both friction and wear reduction of the mixtures with respect to the ester only at 25 °C. The worse tribological behavior at 100 °C could be attributed to the moderate thermal stability of these ionic liquids. Under rolling/sliding conditions, samples displayed similar antifriction and ECR behavior than the base oil at high speeds, changing to a higher friction and lower ECR at low speeds and increasing temperatures. EDX analysis showed mainly the steel disc elements. The XPS oxygen signal showed higher amount of C[dbnd]O bond on the worn surface after reciprocating tests at 25 °C, which could be attributable to IL-surface interaction and can explain the better wear reduction performance

Friction, wear and corrosion behavior of environmentally-friendly fatty acid ionic liquids

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This research deals with the tribological behavior and corrosion performance of three novel fatty acid anion-based ionic liquids (FAILs): methyltrioctylammonium hexanoate ([N8,8,8,1 ][C6:0 ]), methyltrioctylammonium octadecanoate ([N8,8,8,1 ][C18:0 ]) and methyltrioctylammonium octadec-9-enoate ([N8,8,8,1 ][C18:1 ]), employed for the first time as neat lubricant with five different material pairs: steel–steel, steel–aluminum alloy, steel–bronze, steel–cast iron and steel–tungsten carbide. These novel substances were previously obtained from fatty acids via metathesis reactions, identified struc-turally via NMR (nuclear magnetic resonance) and FTIR (Fourier-transform infrared spectroscopy) techniques, and then characterized from a physicochemical (density, water solubility, viscosity, viscosity index and refractive index) and environmental (bacterial toxicity and biodegradability) points of view. The corrosion behavior of the three FAILs was studied by exposure at room temperature, while friction and wear tests were performed with a reciprocating ball-on-disc configuration. The main results and conclusions obtained were: (1) Corrosion in the presence of the three FAILs is observed only on the bronze surface; (2) All FAILs presented similar tribological behavior as lubricants for each tested material pair; (3) XPS (X-ray photoelectron spectroscopy) analysis indicated that the surface behavior of the three FAILs in each material pair was similar, with low chemical interaction with the surfaces