Study of new materials, surfaces and interfaces in tribology

Mención Europeo / Mención Internacional: Concedido[SPA] La presente tesis doctoral recoge los resultados de los trabajos de investigación realizados sobre nanofluidos, nanofases de carbono y nanocomposites de matriz epoxi, su preparación, caracterización y aplicaciones en la reducción de los coeficientes de fricción, las tasas de desgaste y el daño superficial de materiales en distintas condiciones de deslizamiento bajo carga. Se han utilizado cristales líquidos iónicos próticos derivados de ácidos grasos, así como otros líquidos iónicos próticos con aniones carboxilato también biocompatibles como citrato y succinato, para generar nuevos lubricantes base agua, así como nuevas dispersiones conteniendo grafeno y nanodiamantes. La generación de películas finas de lubricante sobre las superficies por evaporación de agua en condiciones suaves, previas al deslizamiento, permite alcanzar prestaciones semejantes a las de los lubricantes puros, con un gran ahorro de líquido iónico. La combinación de líquidos iónicos derivados de imidazolio disponibles comercialmente y grafeno ha dado lugar a dispersiones con un comportamiento reológico sin precedentes, ya que, en función de la concentración de grafeno, su viscosidad se mantiene constante o se incrementa con el aumento de temperatura. Se ha estudiado la aplicación de dispersiones de grafeno en líquidos iónicos como aditivos de una base lubricante libre de aditivos y de un aceite de motor comercial totalmente formulado, mejorando considerablemente sus prestaciones incluso a alta temperatura. Se han obtenido nuevos nanomateriales de matriz epoxi con comportamiento tribológico mejorado. La adición de un líquido iónico de cadena corta, da lugar a un material poroso que libera el líquido iónico bajo carga, presentando un comportamiento autolubricante y de autorreparación del daño superficial. Cuando se añaden líquidos iónicos de cadena larga, se obtienen dispersiones homogéneas que reducen los coeficientes de fricción y previenen el desgaste, incluso en condiciones muy severas de deslizamiento y abrasión. Las nuevas dispersiones de líquido iónico o líquido iónico y grafeno en resina epoxi se han depositado sobre sustrato de resina epoxi sin modificar o de acero al carbono, con el fin de mejorar su resistencia a la fricción y al desgaste, sin modificar las propiedades del material base. En el primero de los casos, se obtienen materiales con un gradiente de composición, ya que los aditivos se localizan allí donde se necesitan, en la capa superficial. En esta investigación ha sido necesaria la utilización de un gran número de técnicas experimentales, de ensayos normalizados y de caracterización de los materiales, así como la colaboración con otros grupos de investigación, tanto nacionales como internacionales.[ENG] The present PhD thesis includes the results of the research works on the preparation and characterization of nanofluids, carbon nanophases and epoxy matrix nanocomposites, and their applications in the reduction of friction coefficients, wear rates and surface damage of materials under different sliding conditions. Protic ionic liquid crystals with anions derived from fatty acids and other protic ionic liquids with biocompatible carboxylate citrate and succinate anions have been used in the development of new water-based lubricants, and in new dispersions containing graphene and nanodiamonds. Thin lubricant films generated, before the sliding, on the surfaces after water evaporation under mild conditions have shown excellent tribological performances, similar to those of the neat ionic liquids, but using a minimum amount of them. The combined use of commercial imidazolium ionic liquids and graphene gives rise to new dispersions with unprecedented rheological behaviour, as they present constant or increasing viscosity values under increasing temperature, as a function of graphene concentration. The new graphene dispersions in ionic liquids have been used as additives in an additive-free lubricant basestock and in a fully-formulated commercial motor oil, achieving good results even at high temperatures. New epoxy matrix nanocomposites have been obtained. The porous material obtained by addition of a short-chain protic ionic liquid shows a self-lubricating and self-healing behaviour. Uniform dispersions obtained when long-chain ionic liquids are added to the epoxy matrix, reduce friction coefficient and prevent wear even under very severe sliding or abrasion conditions. The new dispersions of long-chain ionic liquids or ionic liquids and graphene have been deposited on unmodified epoxy resin or carbon steel substrates to improve their tribological performance without modifying their bulk properties. In the first case, new materials with gradient composition are obtained, where the additives are localized only where they are needed, that is at the material surface. The research work described here makes use of many experimental techniques, standard tests and characterization equipments, and has been possible thanks to the cooperation with national and international research groups.Escuela Internacional de Doctorado de la Universidad Politécnica de CartagenaUniversidad Politécnica de CartagenaPrograma de Doctorado en Tecnologías Industriales por la Universidad Politécnica de Cartagen

Rheological study of new dispersions of Carbon Nanotubes in the ionic liquid 1-ethyl-3-methylimidazolium dicyanamide

Dispersions of three different types of carbon nanotubes in a 1 wt.% proportion in the low viscosity 1-ethyl-3-methylimidazolium ([EMIM][DCA]) ionic liquid have been obtained. The neat ionic liquid presents Newtonian behavior, but the addition of carbon nanotubes increases the viscosity with respect to [EMIM][DCA] in the following order: Single-Walled Carbon Nanotubes (SWCNTs) > aligned Multi-Walled Carbon Nanotubes (aligned-MWCNTs) > Multi-Walled Carbon Nanotubes (MWCNTs), and the resulting fluids show non-Newtonian behavior. SWCNTs and MWCNTs dispersions present shear thinning with increasing shear rate, but a shear thickening effect for aligned-MWCNTs at intermediate shear rate values at room temperature has been observed. This effect disappears at 100 ºC. The thermal response of the viscosity of [EMIM][DCA] and the CNTs-IL dispersions can be fitted to the Arrhenius model. For[EMIM][DCA] and the dispersion with MWCNTs the viscous behavior prevails at low frequencies, with a cross point at a critical frequency value which decreases with increasing temperature. However, the dispersions of SWCNTs and aligned-MWCNTspresent storage modulus values higher than loss modulus in the whole range of frequency.The authors acknowledge the Ministerio de Economía, Industria y Competitividad (MINECO, Spain), the EU FEDER Program (Grants # MAT2014-55384-P and # MAT2017-85130-P), and Fundación Séneca - Agencia de Ciencia y Tecnología de la Región de Murcia “Ayuda a las Unidades y Grupos de Excelencia Científica de la Región de Murcia (Programa Séneca 2014)” (Grant # 19877/GERM/14), for financial support. M.D. Avilés acknowledges a research fellowship (Grant # BES-2015-074836) to MINECO

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)

Nuevo nanocomposite de líquido iónico prótico en matriz epoxi

[ESP] En el presente estudio, se ha preparado un nuevo nanocomposite de matriz epoxi modificada mediante la adición de un líquido iónico prótico. Se han determinado sus propiedades térmicas, dinámicomecánicas y su dureza. También, se ha evaluado su comportamiento frente a fricción y desgaste mediante ensayos tribológicos en configuración de punzón sobre disco, obteniéndose mejoras sustanciales con respecto a la resina epoxi sin modificar. Además, se ha realizado un estudio superficial para determinar la distribución del líquido iónico en el interior de la matriz epoxi. [ENG] In the present study, we have prepared a new nanocomposite of epoxy resin modified by addition of a protic ionic liquid. Its thermal and dynamic-mechanical properties have been determined, and also its hardness. Friction and wear resistance have been evaluated by pin-on-disc tribological test, and if we compare its tribological performance with that of neat epoxy resin, better results have been found. Moreover, we have done a superficial study to determinate the ionic liquid distribution in the epoxy matrix.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

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)

Protic ammonium bio-based ionic liquid crystal lubricants

Bis(2-hydroxyethyl) ammonium stearate (DES) protic ionic liquid crystal (PILC) has been added in 1 wt% and 2 wt% proportion to di-bis(2-hydroxyethyl) ammonium succinate (DSU) protic ionic liquid (PIL) to obtain (DSU+1%DES) and (DSU+2%DES) lubricant blends. The new blends are non-Newtonian fluids with liquid crystalline domains. Addition of (DES) PILC to (DSU) PIL reduces running-in friction coefficient in more than 70% and prevents surface damage, decreasing wear rate in more than one order of magnitude. Optical profilometry, optical and scanning electron microscopy (SEM), energy dispersive (EDX) and X-ray photoelectron spectroscopy (XPS) have been used to analyze surfaces after the tribological tests.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 )”

UAV + BIM: Incorporation of Photogrammetric Techniques in Architectural Projects with Building Information Modeling Versus Classical Work Processes

The current computer technology facilitates the processing of large volumes of information in architectural design teams, in parallel with recent advances in-flight automation in unmanned aerial vehicles (UAVs) along with lower costs, facilitates their use to capture aerial photographs and obtain orthophotographs and 3D models of relief and terrain textures. With these technologies, 3D models can be produced that allow different geometric configurations of the distribution of construction elements on the ground to be analyzed. This article presents the process of implementation in a terrain integrated into the early stages of architectural design. A methodology is proposed that covers the detailed capture of terrain, the relationship with the architectural design environment, and its implementation on the plot. As a novelty, an inverse perspective to the remaining disciplines is presented, from the inside of the object to the outside. The proposed methodology for the use of UAVs integrates terrain capture, generation of the 3D mesh, superimposition of environmental realities and architectural design using building information modeling (BIM) technologies. In addition, it represents the beginning of a line of research on the implementation of the plot and the layout of foundations using UAVs. The results obtained in the study carried out in three different projects comparing traditional technologies with the integration of UAVs + BIM show a clear improvement in the second option. The use of new technologies applied to the execution and control of work not only improves accuracy but also reduces errors and saves time, which undoubtedly indicates significant savings in costs and deviations in the project.This work has been supported by the Ministerio de Ciencia, Innovación y Universidades (Spain), project RTI2018-096219-B-I00. Project cofinanced with FEDER funds

The Dialogue between Ancient and Modern Materials in the Restoration of a Collapsed Ancient Chapel

While facing a restoration of an ancient building, sometimes a reconstruction is needed. The decision to use modern materials could be quite conflictive, especially when the building is to be in use once again and the visitors see the outcome. This was the case of the Chapel of the Holy Sepulchre, Orihuela (Alicante). It was built as a satellite cult place from the abbey of San Francisco, and it was placed as a Calvary at the top of a hill close to the main building. Over the years, this building became part of the neighbourhood’s identity and one of the most important anchor points for the inhabitants of the area. Neglected maintenance made the building collapse at the end of the 1990s. The City Council of Orihuela acquired the building in 2007 and planned to restore it, but architects faced a problem regarding restoration, as most parts of the building had collapsed. The restoration process of the chapel, especially in terms of structure, is based on the relation between modern and traditional materials, a final touch that did not change the feeling of identity that the inhabitants once had over the original chapel

Energy Efficiency and Economic Viability as Decision Factors in the Rehabilitation of Historic Buildings

The restoration of historical buildings often implies a change in the main use of the building so that it can once again become a part of people’s lives. Among the interventions needed to adapt the buildings to their new purpose, improving the energy performance is always a challenge due to their particular construction solutions and the influence that these improvements can have on their protected elements. The regulations in force in European Union (EU) member states leave a gap in how the energy performance evaluations in these types of buildings can be defined, and even exclude them from the process. However, rehabilitation of buildings is always seen as an opportunity, because it allows the building to once again be useful to society and play an important role in people’s lives. At the same time, it can also improve their performance and allow benefits to be gained from their use through a reduction in maintenance costs. In the rehabilitation process, the economic viability of the renovation plays a fundamental role which must be compared, in the case of protected buildings, to its impact on the architecture of the building. Since 2002, the EU has issued directives with the aim that countries should define objective methods to improve the energy performance of buildings and, in recent times, methods that demonstrate the amortization of such improvements. Within the process of implementing the new methodologies adapted to the EPBD, Spain was one of the last EU countries to define a process for the energy assessment of existing buildings, introducing an analysis of the economic viability of the construction improvements suggested in the process. The objective of this research was to describe the decision-making process during the evaluation of the feasibility of introducing construction improvements to the energy performance of two catalogued historic buildings located in a warm climate. The estimated energy consumption was evaluated, the net present value (NPV) and the payback period of the investment calculated, and the results obtained were compared with the real energy consumption. At the end of the process, it can be said that the methodologies adopted in Spain offer results that can lead designers to make wrong decisions that may affect the protected heritage values of these buildings

Identificación de zonas de riesgo ambiental en la ciudad de Murcia usando índices de contaminación y SIG

The objective of this study was to demonstrate the usefulness of GIS and pollution indexes to identify environmental risk zones affected by heavy metals in urban areas. The study area is located in the city of Murcia and surrounding (SE, Spain). The concentrations of sCr, Zn, Cu, Pb, Mn, Ni and Cd in 221 soil samples were determined, and five pollution indexes calculated. After an analysis of each index and a comparison between them, it was selected the pollutant load index (PLI), for the following reasons: 1 provided a good spatial distribution of the areas of highest risk, 2 all metals contributed in a similar way to the index value, and 3 the index includes background concentrations in its calculation, which allowed determine the level of metal enrichment of each sample. After selecting the index, a GIS was used to create a spatial distribution map ajusting the SIG parameters to obtain a proper definition of the areas with the highest environmental risk, in this case eight areas were identified. Therefore, the calculation of pollution indexes and subsequent integration into a SIG is an appropriate tool for identifying environmental risk areas by heavy metals in urban settlements