Ionic liquids as lubricants of metal -polymer contacts. Preparation and properties of the first dispersions of ionic liquids and nanoparticles in polymers

[SPA] Los líquidos iónicos son fluidos de altas prestaciones con un amplio rango de estabilidad térmica que encuentran numerosas aplicaciones en ingeniería. Aunque se han utilizado como lubricantes de contactos metal-metal, metal-cerámico y cerámico-cerámico, en este trabajo presentamos el primer estudio acerca del empleo de los líquidos iónicos como lubricantes puros en contactos polímero-acero. Se ha comprobado la eficacia de los líquidos iónicos para reducir los coeficientes de fricción y las tasas de desgaste en una variedad de contactos acero-polímero y en un amplio rango de temperaturas, incluyendo condiciones criogénicas. Como aditivo de polímeros, se han obtenido las primeras dispersiones de líquidos iónicos en polímeros termoplásticos y termoestables y se han determinado sus propiedades térmicas, mecánicas y tribológicas. Se ha estudiado el efecto del contenido de líquido iónico en las propiedades tribológicas de las nuevas dispersiones y su influencia sobre los mecanismos de desgaste mediante microscopía electrónica de barrido (SEM) y microanálisis (EDS). Las nuevas dispersiones muestran valores de fricción y desgaste más bajos que los polímeros puros. Esta reducción de fricción y desgaste puede llegar a superar el 79%.Para ciertos polímeros termoplásticos como poliestireno y poliamida 6, las nuevas dispersiones preparadas muestran valores de fricción y desgaste inferiores a los obtenidos cuando se utiliza el líquido iónico puro como lubricante externo del par acero-polímero.Se han utilizado nanopartículas de óxido de cinc como aditivos de policarbonato con el fin de mejorar su resistencia al desgaste. Se han obtenido distintas dispersiones con contenido variable de nanopartículas y se ha estudiado el efecto de la concentración de óxido de cinc en las propiedades térmicas, mecánicas y tribológicas. Se ha comprobado que cuando dichas partículas se modifican mediante la adición de un líquido iónico, se obtienen nuevos nanocomposites polímero-líquido iónico-nanopartícula con propiedades tribológicas mejoradas. Finalmente, para entender los procesos que tienen lugar en la interfase nanopartícula-líquido iónico, se han estudiado las interacciones entre las nanopartículas y el líquido iónico. Los cambios superficiales, morfológicos y estructurales se han caracterizado mediante microscopía electrónica de transmisión (TEM), microanálisis (EDS), análisis de superficies (XPS) y difracción de rayos X (XRD). Los resultados ponen de manifiesto la importancia de la influencia de las condiciones del proceso sobre la estabilidad del anión presente en el líquido iónico.[ENG] Room-temperature ionic liquids (ILs) are high performance fluids that stand out because of a wide range of functional properties and exhibit a great potential for engineering applications. Although they have been employed as lubricants in metal-metal, metal-ceramic and ceramic-ceramic contacts, in this thesis we present the first study about the use of ILs as pure lubricants in polymer/steel contacts. The tests have established the efficacy of the ILs to reduce friction coefficient and wear rates in a variety of kinds of contacts, and criogenic to high temperature performance. Novel dispersions of ILs in polymers have been obtained with epoxy resin and thermoplastics as matrix. Therefore, the thermal, mechanical and tribological properties of the materials have studied and are discussed in the present thesis. Furthermore, the contents of ILs in the polymer matrix have been studied in relation to the tribological properties using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectrometry (EDS), the wear mechanisms that operated in the contacts were established. The novel dispersions showed a reduction in the friction coefficient and wear in comparison with neat polymers, reaching in some cases a decrease of 79%. In the case of thermoplastics such as polystyrene and polyamide 6, the new dispersions showed a reduction in friction coefficient and wear in the same range as that of the ILs when used as external lubricants in the steel/polymer contact. In addition nanoparticles of zinc oxide were used to obtain polycarbonate based nanohybrids with the purpose of improving the tribological properties. Novel nanohybrids of zinc oxide and modified zinc oxide were obtained. The mechanical, thermal and tribological properties were studied. The results of experiments clearly demonstrated that the use of ILs modifies the shape and size of the ZnO nanoparticles, increasing the tribological properties of the novel nanohybrids. Different techniques such as EDS, Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectrometry (XPS) were used to examine and establish the surface interactions and mechanism that operated between ILs and ZnO. In summary, the results reveal the importance of the processing parameters on the stability of the nature of the anion in the ILs.Universidad Politécnica de CartagenaPrograma de doctorado en Tecnologías Industriale

New graphene/ionic liquid nanolubricants

In this work, we have prepared new graphene/ionic liquid dispersions by adding a 0.1wt.% proportion of 1-2 layers graphene (G1) or 1-10 layers graphene (G2) to the ionic liquid 1-octyl-3-methylimidazolium tetrafluoroborate (IL). The new dispersions (IL+G1) and (IL+G2) have been used as external lubricants in polymer-steel and ceramic-steel contacts. For AISI 316L stainless steel/epoxy resin, the order of friction reduction is (IL+G2)>IL>(IL+G1). The wear reducing order is the same, as abrasive wear takes place for (IL+G1), while G2 prevents any degree of surface damage on both materials, even the very mild wear observed for neat IL. The poor performance of G1 is related to the formation of abrasive graphene-IL aggregates. The (IL+G2) dispersion also shows superior friction reducing and anti-wear behavior under more severe contact conditions, for AISI316L against sapphire.The authors thank the financial support of the Ministerio de Economia y Competitividad (MINECO, Spain; FEDER, EU) (Grant MAT2014-55384-P). “Este trabajo es resultado de los proyectos de investigación (19292/PI/14, 19544/GERM/14 and 19877/GERM/14) financiados por la Fundación Séneca-Agencia de Ciencia y Tecnología de la Región de Murcia en el marco del PCTIRM2011-2014”. N. Saurin is grateful to MINECO (Spain) for a FPI research Grant (BES-2012-056621)

Study of the abrasion resistance of new epoxy (ER) – ionic liquid (IL) materials with self-healing ability

In the present work, new epoxy resin (ER) – ionic liquid (IL) dispersions have been obtained and their abrasion resistance has been determined by multiple scratch tests. The IL was added in a range of concentrations between 7 and 12 wt. %.After the scratch tests, the viscoelastic recovery and healing ability of the damaged surface has been monitorized using optical and electronic microscopy and profilometry. The results are discussed on the basis of the curing procedure and are related to mechanical, thermal and dynamic-mechanical properties, and to surface porosity of the new dispersions.The authors acknowledge the financial support of the Ministerio de Economía y Competitividad (MINECO, Spain) (Grant # MAT2014-55384-P). N. Saurín is grateful to MINECO (Spain) for a FPI research (Grant # BES-2012-056621)

Tribological study of the AISI316L/Sapphire contact with self-lubricating films of protic ionic liquids

Ionic liquids have shown an outstanding performance as lubricants in different contacts. Protic ammonium carboxylate ionic liquids (PILs), both neat and as additives in water, are being studied as friction-reducing and wear prevention lubricants in stainless steel-sapphire contacts. When a PIL was used as additive in water, the high temperature reached at the sliding contact produced the evaporation of water and the formation of a low friction PIL boundary layer. In the present study, the formation of the PIL boundary layer on AISI316L stainless steel under static conditions is described and its lubricating performance against sapphire balls has been studied. The effect of relative humidity has been studied using a vacuum chamber. The results described in the present study show a good tribological performance of these thin surface films, in pin-on-disc tests, reducing the running-in period of high friction coefficient, preventing wear and reducing the volume of lubricant with respect to the results obtained when water+1%PIL and neat PIL are used as lubricants.Competitividad (MINECO, Spain) (MAT2011-23162 and MAT2014-55384-P) for financial support. T. Espinosa is grateful to the Ministerio de Educación, Cultura y Deporte (MECD, Spain) for a research Grant (AP2010-3485)

Bio-based ionic liquid crystal for stainless steel-sapphire high temperature ultralow friction

In the present work, the biobased protic ionic liquid crystal bis(2-hydroxyethyl) ammonium palmitate (DPA) has been studied as neat lubricant under linear reciprocating sliding at 75 °C, in the liquid crystalline region, and at 110 °C, above its melting point. Three different tribopairs have been studied using AISI 52100 steel, AISI 316L stainless steel and sapphire balls against AISI 316L disks. Tribological results at 75 °C are in agreement with the different sliding pairs and contact conditions. At 110 °C, a sharp friction coefficient reduction to reach an ultralow steady state value of 0.007–0.009, is observed for the sapphire-AISI 316L contact. Wear rate is also reduced in one order of magnitude. Results are related to water content in DPA, as determined by TG-MS. Wear mechanism are discussed upon the basis of optical and scanning electron microscopy (SEM/EDX) and of surface analysis by XPS.This research was funded by Spanish Ministerio de Ciencia e Innovación, Agencia Estatal de Investigación (AEI), and the European Union FEDER Program (Grant # MAT2017–85130-P). “Este trabajo es resultado de la actividad desarrollada en el marco del Programa de Ayudas a Grupos de Excelencia de la Región de Murcia, de la Fundación Seneca, Agencia de Ciencia y Tecnología de la Región de Murcia (Grant #19877/GERM/15)”

Influence of temperature on PA 6−steel contacts in the presence of an ionic liquid lubricant. Poster

Room−temperature ionic liquids (ILs) are salts with a melting point lower than room temperature and are called green solvents because they have properties such as: ♦ Non−flammability, ♦ Negligible volatility, and ♦ High thermal stability. The high thermal stability range (from −74 ºC to 370 ºC in our case) of ILs makes them suitable candidates as high temperature and extreme temperature lubricants. In this work we present the mechanical and tribological properties of polyamide 6−IL dispersion (PA 6+3wt.% IL) under variable load and temperature conditions, against AISI 52100 steel or AISI 316L stainless steel.We wish to thank MEC (Spain) and the EU FEDER program (MAT2002−03947 and MAT2005−00067) and the Fundación Séneca (Región de Murcia, Spain) (PI/00447/FS/04) for financial support. A.E. Jiménez is grateful for a research grant

Antiwear performance of ionic liquid+graphene dispersions with anomalous viscosity-temperature behavior

New dispersions of few-layers graphene (G) in 1-ethyl-3-methylimidazolium ([EMIM]) ionic liquids (ILs) with dicyanamide ([DCA]) or bis(trifluoromethylsulfonyl)imide ([TFSI]) anions have been obtained by mechanical mixing and sonication. IL+0.5 wt% G dispersions show constant viscosity values from 357K (for IL = [EMIM][DCA]) or from 385K (for IL = [EMIM][TFSI]) to 393K. IL + G dispersions with G > 0.5 wt% show linear viscosity increases with increasing temperature, from 306K (for [EMIM][DCA]+1 wt%G) and from 330K to 393K (for [EMIM][TFSI]+0.75 wt%G and [EMIM][TFSI]+1 wt%G). Addition of graphene improves the poor wear reducing performance of [EMIM][DCA], and prevents surface damage on steel when added to [EMIM][TFSI]. Graphene increases the load-carrying ability of ILs, forms a surface layer on the sliding path and retains wear debris, preventing the formation of large abrasive particles.Ministerio de Economía, Industria y Competitividad (MINECO, Spain), EU FEDER Program (Grant # MAT2017-85130-P) Este trabajo es resultado de la actividad desarrollada en el marco del Programa de Ayudas a Grupos de Excelencia de la Región de Murcia, de la Fundación Séneca, Agencia de Ciencia y Tecnología de la Región de Murcia (Grant # 19877/GERM/15) M.D. Avilés ha recibido una beca del MINECO (BES-2015-074836)

Ionanocarbon lubricants. The combination of ionic liquids and carbon nanophases in tribology

The present overview will focus on the tribological applications of what we have called ionanocarbon lubricants, that is, the combination of carbon nanophases (graphene, carbon nanotubes, nanodiamonds, carbon nanodots) and room-temperature ionic liquids in new dispersions, blends, or modified nanostructures and their use in tribology, lubrication, and surface engineering as friction-reducing, antiwear, and surface-protecting agents in thin films and composite materials. Further research lines and factors that limit the practical applications of the outstanding research results are also highlighted. The very recent results in these lines of research make this a necessary brief review.The authors wish to thank the financial support of the Ministerio de Economía y Competitividad (MINECO, Spain) (MAT2014-55384-P). “Este trabajo es resultado de la actividad desarrollada en el marco del Programa de Ayudas a Grupos de Excelencia de la Región de Murcia, de la Fundación Séneca, Agencia de Ciencia y Tecnología de la Región de Murcia (19877/GERM/15)”. María-Dolores Avilés is grateful to MINECO for aresearch grant (BES-2015-074836)

Nuevos materiales con capacidad de autorrecuperación

[ESP] En el presente trabajo se describe el efecto auto-reparador del daño superficial de tipo abrasivo creado sobre una resina epoxi (RE) modificada mediante la dispersión de líquido iónico (LI) en su matriz. Se han preparado distintos nanocomposites con diferentes cantidades de LI (7-12% en peso). Se ha comprobado la resistencia a la abrasión de RE modificada con distintas concentraciones de LI mediante ensayos de multirrayado bajo carga constante. En el caso de RE sin aditivos, la recuperación viscoelástica tiene lugar durante los primeros 30 minutos. En el caso de las resinas con distintos contenidos de LI, ésta continúa en el tiempo. [ENG] The present work describes the self-healing of abrasions surface damage in epoxy resin modified by dispersed ionic liquid phase. Different content ionic liquid-epoxy resin nanocomposites (7-12% wt.) have been prepared. The abrasion resistance of epoxy resin with different content of ionic liquid was determined by multiple scratching under constant load. In the case of neat epoxy resin, viscoelastic recovery process ends after 30 min. For the ionic liquid-epoxy resin nanocomposites, the recovery process continues with time.Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT), Escuela Técnica Superior de Ingeniería Agronómica (ETSIA), Escuela Técnica Superior de Ingeniería Industrial (ETSII), Escuela Técnica Superior de Arquitectura y Edificación (ETSAE), Escuela Técnica Superior de Ingeniería de Caminos, Canales y Puertos y de Ingeniería de Minas (ETSICCPIM), Facultad de Ciencias de la Empresa (FCCE), Parque Tecnológico de Fuente Álamo (PTFA), Vicerrectorado de Estudiantes y Extensión de la UPCT, Vicerrectorado de Investigación e Innovación de la UPCT, y Vicerrectorado de Internacionalización y Cooperación al Desarrollo de la UPCT

Nuevos nanocomposites grafeno/líquido iónico en matriz epoxi

En el presente trabajo se han preparado nanocomposites de matriz epoxi (RE) modificada mediante la adición de partículas de grafeno 1 o 2 capas (PG) y mediante la adición de PG y del líquido iónico tetrafluoroborato de 1-metil-3-octilimidazolio (LI). Se han preparado también dispersiones de LI con PG con el fín de observar su comportamiento como lubricante externo. Se han realizado ensayos de punzón sobre disco con el fin de estudiar la resistencia al desgaste adhesivo y abrasivo de las muestras. Se han estudiado los mecanismos de daño superficial mediante microscopía electrónica de barrido y perfilometría óptica, así como las propiedades térmicas de las nuevas dispersiones.Centro Universitario de la Defensa. Escuela de Turismo de Cartagena. Escuela Técnica Superior de Ingeniería Industrial UPCT. Escuela Técnica Superior de Ingeniería de Telecomunicación (ETSIT). Escuela de Ingeniería de Caminos y Minas (EICM). Escuela de Arquitectura e Ingeniería de Edificación (ARQ&IDE). Parque Tecnológico de Fuente Álamo. Navantia. Campus Mare Nostrum. Estación Experimental Agroalimentaria Tomás Ferr