Design and Characterization of Lubricants Based on Functionalized Nanoparticles

The main objective of this PhD thesis is to design and characterize efficient nanolubricants based on three polyalphaolefins (PAOs) and nanoparticles (NPs) of metal oxides or ceramics coated with organic acids for wind turbine gearboxes and electric transmissions of electric vehicles. First, preliminary tests and an in-depth literature survey on the time stability and tribological behavior of nanodispersions containing chemically modified nanoadditives were performed. Then, the thermophysical and tribological properties of PAO nanolubricants containing coated NPs (ZnO-OA, TiO2-OA, or SiO2-SA) were evaluated; in addition, possible tribological mechanisms were analyzed by confocal Raman microscopy. All the coated NPs studied improve the tribological behavior of their base oil, being the best the SiO2-SA NPs

Chemically modified nanomaterials as lubricant additive: time stability, friction, and wear

This work reviews the results on the temporal stability of nanodispersions containing chemically modified nanoadditives: carbon-based nanomaterials, metals, metal oxides, metal sulfides, nanocomposites, among others. Morphology, size, coating type and concentration of the NPs as well as the viscosity of the base oil are the main characteristics that affect stability. Coated spherical NPs with mean diameter lower than 20 nm are the most common among those which led to nanolubricants with stabilities longer than two months. The tribological results of the nanolubricants with stabilities higher than one month are also reviewed. Regardless the base oil, chemically modified nanoparticles reduced wear more than friction, reaching reductions of friction up to 75% and wear volume up to 99%. As for the tribological mechanisms involving chemically modified nanoparticles, the formation of adsorbed or tribochemical reaction films on worn surfaces were reported more oftenThis work is supported by MCIN/AEI/10.13039/501100011033 and by the European Regional Development Fund (ERDF, FEDER in Spanish) through the ENE2017-86425-C2-2-R and the PID2020-112846RB-C22 projects as well as by Xunta de Galicia (ED431C 2020/10). JMLDR acknowledges the grant of the Margarita Salas program, funded by MCIN/AEI/10.13039/501100011033 and “NextGenerationEU/PRTR”S

Double hybrid lubricant additives consisting of a phosphonium ionic liquid and graphene nanoplatelets/hexagonal boron nitride nanoparticles

Tribological performance of polyalphaolefin 32, PAO, is investigated by adding two nanomaterials (graphene nanoplatelets, GnP, and hexagonal boron nitride nanoparticles, h-BN) and an ionic liquid ([P6,6,6,14][DEHP], IL1, [P2,4,4,4][DEP], IL2, or [P6,6,6,14][(iC8)2PO2], IL3). Designed double hybrid nanodispersions are PAO/1 wt% ILX/0.05 wt% GnP/0.1 wt% h-BN (X = 1, 2 or 3). The best anti-friction behavior corresponds to PAO/IL3/GnP/h-BN (40% reduction compared to that achieved with PAO). Anti-wear behavior is similar for the three double hybrid nanodispersions. Roughness of the worn surface tested with PAO is higher than that obtained for each of the nanodispersions. Tribo-film formation and repair effect on worn surfaces due to ILs and nanoparticles are revealed. Some positive synergies were found between each IL and GnP/h-BN as hybrid PAO additivesMinistry of Science and Innovation (Spain) and the European Regional Development Fund supported this work through the project ENE2017-86425-C2-2-R. This research was also financially supported by Xunta de Galicia, Spain (Grant ED431C 2020/10)S

Innovation in vocational education and training (vet) in Galicia (Spain): relevant projects and initiatives with didactic and transfer potential

Hoxe en día falar de proxectos de innovación educativa non é algo novidoso nas diferentes etapas educativas. Sen embargo, aínda segue a ser unha cuestión pouco visibilizada na Formación Profesional (FP) que, en moitas ocasións, queda reducida a propostas relacionadas co uso de recursos TIC nos procesos de ensino-aprendizaxe. Ante isto, podemos preguntarnos cal é a situación dos proxectos e potencial de innovación naqueles estudios de vocación eminentemente práctica en Galicia. Este traballo pretende achegarnos ao que se está a facer no ámbito da innovación nos centros de FP galegos, unha realidade pouco visibilizada e estudada que, sen embargo, recolle unha gran diversidade de accións, iniciativas e proxectos en materia de innovación educativa. Para iso, levouse a cabo unha investigación descritiva, de carácter exploratorio e eminentemente cualitativa na que, a partir da análise de fontes documentais primarias, como son as distintas resolucións das convocatorias anuais de premios á innovación en FP, se pretendeu responder ás seguintes preguntas de investigación: estase innovando nos centros de FP? Que tipo de proxectos son os considerados innovadores polas administracións e premiados? Que familias profesionais son as involucradas? Que tipo de centros participan máis da innovación? Analízanse así, as convocatorias de premios á innovación en FP dos anos 2019 e 2020 na comunidade autónoma de Galicia, na cal se presentaron en total 144 propostas innovadoras, das cales foron inalmente premiadas, 86. A modo de conclusión, realízase unha análise crítica da situación actual da innovación na FP en Galicia, aportando referentes a ter en conta e valorándoa á luz do papel que debe xogar a FP no marco da construción dunha cidadanía so século XXIToday, talking about educational innovation projects is not something new in the different educational stages. However, it remains a topic of low visibility in Vocational Education and Training (VET) which, in many cases, is reduced to proposals related to the use of ICT in teaching-learning processes. Given this, we wondered what is the situation of the innovation in VET in Galicia (Spain). This work aims to show what is being done in terms of innovation in Galician vocational training schools, which is a low visible and studied reality that however, includes a wide variety of actions, initiatives and projects in the ield of educative innovation. To this end, a descriptive, exploratory and eminently qualitative research was carried out in which, based on the analysis of primary documentary sources, such as the resolutions of the annual innovation in VET awards, was intended to answer research questions such as the following: Are Galician VET Schools innovating? What kind of projects are considered innovative by the administrations and inally, awarded? What professional ields are involved? What kind of VET schools are most involved in innovation? Thus, the resolutions of the annual VET innovation awards in 2019 and 2020 in the autonomous community of Galicia are analyzed, in which a total of 144 innovative proposals were presented, of which, 86 were inally awarded. To conclude, a critical analysis is made of the current situation of innovation in VET in Galicia, providing references to take into account and assessing it in light of the role that VET has to play in the construction of the citizenship of the 21st centuryS

Tribological enhancement of potential electric vehicle lubricants using coated TiO2 nanoparticles as additives

This work presents the antifriction and antiwear properties of TiO2 nanoparticles coated with oleic acid, TiO2-OA, as additives of a low viscosity polyalphaolefin base oil, PAO8. To find the optimal concentration of nanoadditives that minimize friction and wear, four PAO8 based nanodispersions were formulated: PAO8 + 0.10 wt% TiO2-OA, PAO8 + 0.25 wt% TiO2-OA, PAO8 + 0.35 wt% TiO2-OA and PAO8 + 0.50 wt% TiO2-OA. Tribological experiments were performed under pure sliding and rolling-sliding conditions at 120 °C, with the four formulated nanolubricants and with PAO8 base oil. All the nanolubricants showed lower friction coefficients than that obtained with the PAO8 base oil, reaching maximum reductions for the 0.35 wt% TiO2-OA nanolubricant, for both types of test conditions. The tribological specimens tested under pure sliding conditions with the nanolubricants showed fewer wear than those tested with PAO8, finding the highest wear decreases also with the PAO8 + 0.35 wt% TiO2-OA nanolubricant, being 26 %, 65 % and 73 %, in wear track width, depth and area, in that order. Through Raman microscopy and roughness study of the worn samples, it can be inferred that tribofilm, mending and polishing mechanisms occur. Moreover, the thermal conductivity of the optimal nanolubricant (0.35 wt%) was measured at 20, 30, 40 and 50 °CThis research is supported by Xunta de Galicia (ED431C 2020/10), by MCIN/AEI/10.13039/501100011033 through the PID2020-112846RB-C22 project and by LAETA, Portugal under project UID/50022/2020. JMLDR is grateful for financial support through the Margarita Salas programme, funded by MCIN/AEI/10.13039/501100011033 and “NextGenerationEU/PRTR”. FM acknowlegdes a IACOBUS grant to the European Grouping for Territorial Cooperation Galicia-Norte de Portugal (GNP-EGTC). Furthermore, authors also thank Repsol Lubricants for supplying us the PAO8 base oil and recognize the support of the RIAIDT-USC analytical skillsS

ZnO nanoparticles coated with oleic acid as additives for a polyalphaolefin lubricant

In this work, ZnO nanoparticles (NPs) were successfully synthesized and coated with oleic acid (OA). The mean diameter of these NPs (ZnO-OA) was around 11.5 nm, their core was characterized by XRD and their coating by FTIR and Raman. Homogeneous dispersions at different concentrations (0.10, 0.25, 0.50, 0.75 and 1.00 wt%) of ZnO-OA in polyalphaolefin 40 (PAO40) oil were thermophysically and tribologically characterized. Both density and viscosity values increased with the concentration of NPs, reaching relative increments of 0.5% and 4.0%, respectively, for the 1 wt% nanodispersion. Tribological tests were performed at 353.15 K using an Anton Paar MCR 302 rheometer equipped with a tribological ball-on three-pins configuration testing module. Regarding the tribological behavior, the optimal concentration was 0.25 wt% of ZnO-OA (25% of reduction in the friction coefficient and 82% wear reduction in terms of cross sectional area, respect to those obtained with the neat base oil). The rolling mechanism owing to the spherical shape of the nanoadditives, transforming sliding friction into rolling friction, and the mending effect could explain the better tribological performance of nanolubricants with respect to that of neat PAO40. In addition, the presence of PAO40, ZnO-OA NPs and iron oxides was evidenced from confocal Raman microscopy on the worn surfaces obtained from tribological test with PAO40 + 0.25 wt% ZnO-OA dispersionFunding for this work has been provided by the Ministry of Science, Innovation and Universities of Spain and the European Regional Development Fund (ERDF, FEDER in Spanish) through the ENE2017-86425-C2-2-R project, and by the Xunta de Galicia through ED431C 2020/10S

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio

Effect of the addition of coated SiO2 nanoparticles on the tribological behavior of a low-viscosity polyalphaolefin base oil

This work reports tribological properties of PAO6 containing SiO2 nanoparticles modified with stearic-acid (SiO2-SA) as additives at concentrations (0.05, 0.10, 0.20, 0.30) wt% and the same concentration of SA as a dispersant. Tribological experiments were performed at 120 °C in pure sliding and rolling-sliding conditions (5% slide-to-roll ratio). All nanolubricants have better anti-friction capabilities than PAO6. The optimum concentration for friction reduction was 0.30 wt% for both tribological conditions. The best anti-wear results for the specimens tested in pure sliding conditions were achieved with PAO6 + 0.20 wt% SiO2-SA with reductions of 55%, 86% and 92%, in wear track width, wear track depth and wear area, respectively. Tribological mechanisms of the nanoparticles have been analyzed through roughness measurements, concluding that polishing, tribofilm and adsorption of the additives occurThis research is supported by Xunta de Galicia (ED431C 2020/10), by MCIN/AEI/10.13039/501100011033 through the PID2020-112846RB-C22 project and by LAETA, Portugal, under project UID/50022/2020. JMLdR is grateful for financial support through the Margarita Salas program, funded by MCIN/AEI/10.13039/501100011033 and “NextGenerationEU/PRTR”. FM acknowledges a IACOBUS grant to the European Grouping for Territorial Cooperation Galicia-North of Portugal (GNP-EGTC). Furthermore, authors are also grateful to Repsol Lubricants for providing the PAO6 base oil and to RIAIDT-USC for its analytical facilitiesS

High-Pressure Thermophysical Properties of Eight Paraffinic, Naphthenic, Polyalphaolefin and Ester Base Oils

In this work, the thermophysical properties of four mineral (paraffinic and naphthenic) and four synthetic (polyalphaolefin and ester) base oils are measured. Knowledge of these properties is of vital importance for the correct and optimal formulation and design of lubricants, and for the development of equations of state and transport models that adequately represent their properties. Density, isothermal compressibility, thermal expansion coefficient, dynamic viscosity, pressure–viscosity coefficient, and contact angle were determined. To carry out this work, a pρT apparatus, a rotational viscometer, a falling body viscometer, and a contact angle analyzer were used. Highest densities were found for the polyalphaolefin and ester synthetic oils, increasing around 5% from 0.1 to 100 MPa for all the base oils. The density of the synthetic oils is less dependent on temperature changes. For the expansivity and compressibility of all the base oils, decreases with pressure of up to 35% and 45% were observed. From the contact angle measurements, it was observed that base oils with a higher viscosity grade have a worse wetting. The greatest effect of pressure on the dynamic viscosity was obtained for the naphthenic mineral oil and the lowest effect for the polyalphaolefin oil. Paraffinic and naphthenic oils present the highest universal pressure–viscosity coefficients

High-Pressure Thermophysical Properties of Eight Paraffinic, Naphthenic, Polyalphaolefin and Ester Base Oils

In this work, the thermophysical properties of four mineral (paraffinic and naphthenic) and four synthetic (polyalphaolefin and ester) base oils are measured. Knowledge of these properties is of vital importance for the correct and optimal formulation and design of lubricants, and for the development of equations of state and transport models that adequately represent their properties. Density, isothermal compressibility, thermal expansion coefficient, dynamic viscosity, pressure&ndash;viscosity coefficient, and contact angle were determined. To carry out this work, a p&rho;T apparatus, a rotational viscometer, a falling body viscometer, and a contact angle analyzer were used. Highest densities were found for the polyalphaolefin and ester synthetic oils, increasing around 5% from 0.1 to 100 MPa for all the base oils. The density of the synthetic oils is less dependent on temperature changes. For the expansivity and compressibility of all the base oils, decreases with pressure of up to 35% and 45% were observed. From the contact angle measurements, it was observed that base oils with a higher viscosity grade have a worse wetting. The greatest effect of pressure on the dynamic viscosity was obtained for the naphthenic mineral oil and the lowest effect for the polyalphaolefin oil. Paraffinic and naphthenic oils present the highest universal pressure&ndash;viscosity coefficients