Recubrimientos protectores nanoestructurados preparados por magnetron sputtering

La presente tesis ha consistido en la obtención de materiales en forma de película delgada con propiedades protectoras con la finalidad de ser utilizados en distintas aplicaciones: lubricantes, biológicas y resistencia a la oxidación a altas temperaturas. Dichas películas se han obtenido mediante la técnica de deposición en fase vapor magnetron sputtering (o pulverización catódica). Las propiedades de las mismas se han desarrollado mediante la selección de las condiciones de síntesis más adecuadas tras un proceso iterativo de optimización del tamaño, distribución y naturaleza de las fases constituyentes a escala nanométrica. En este trabajo se han preparado los siguientes sistemas orientadas a tres campos de aplicación distintos: Recubrimientos protectores lubricantes basados en WSex: los materiales obtenidos presentan valores de fricción por debajo de 0.1 y tasas de desgaste del orden de 10-7 mm3/Nm, independientemente de la atmósfera circundante. En atmósfera inerte se obtuvieron coeficientes de fricción tan bajos como 0.05 y tasas de desgaste de 2•10-8 mm3/Nm. Estas propiedades se han conseguido gracias al control de la composición química del recubrimiento mediante la aplicación de un voltaje negativo variable durante la síntesis. De este modo, se ha conseguido una zona inferior rica en W que proporcionaba un excelente soporte mecánico y buena adhesión, y una zona superior rica en selenio formada por un nanocomposite de dos fases, una amorfa rica en W y otra nanocristalina rica en selenio. Mediante técnicas de microscopía electrónica de transmisión se pudo determinar que la fase nanocristalina es la responsable de la baja fricción mediante un alineamiento de los planos cristalinos en la dirección del desplazamiento, de tal manera que se minimizaba la fricción y se propiciaba un fácil deslizamiento. Recubrimientos protectores basados en a-C(Ag): en este caso se han desarrollado recubrimientos basados en carbono amorfo dopado con Ag. Las propiedades tribológicas en seco no presentan cambios significativos con el contenido de Ag, aunque existe un cierto descenso del coeficiente de fricción respecto a la referencia no dopada (0.16 vs 0.22) y por otro lado, un ligero incremento de la tasa de desgaste (de 1.5•10-7 a 3•10-7 mm3/Nm). Cuando los ensayos se ejecutaron en medio biológico tampoco se observó dependencia alguna con el contenido de Ag aunque el desgaste fue mucho menor (del orden de 10-8 mm3/Nm) atribuible a la formación de una capa superficial protectora de moléculas de proteínas. Asimismo se han realizado estudios con cultivos bacterianos (E. Coli) en los que se constató el efecto bactericida de la plata gracias a la liberación de iones Ag+ al medio acuoso que afecta a procesos vitales de las bacterias. Recubrimientos protectores basados en CrAl(Y,Zr)N: la incorporación de Y o Zr en recubrimientos de CrAlN permitió incremental la resistencia a la oxidación hasta temperaturas de 1000 ºC siendo el Y el dopante más favorable. Por otro lado se prepararon dos conjuntos con distintos contenidos de Al (~5 y ~11 % at.) e Y (~2 y 4-5 % at.) con distintas condiciones de síntesis. El estudio reveló que la nanoestructura, composición química y naturaleza de los sustratos determina la resistencia a la oxidación. Así, a pesar de que un aumento de la cantidad de Al presuponía una mejora del comportamiento, las capas de menor porcentaje (siempre que tuvieran itrio) resultaron ser las mejores. Las investigaciones llevadas a cabo para determinar su comportamiento evidenciaron que los recubrimientos de bajo contenido de Al presentaban un crecimiento cuasi-epitaxial de capas de fcc-CrN que se alternan con otras de fcc-CrAlN o fcc- CrYN/YN, mientras que los recubrimientos de alto contenido de Al estaban formados por capas cristalinas de fcc-CrN que se alternaban con capas predominantemente amorfas de nitruros mixtos de Cr, Al e Y. El mecanismo de protección de los recubrimientos CrAlYN se debe principalmente a la formación de una capa de pasivación de óxidos mixtos de cromo y aluminio que evita la difusión del oxígeno hacia el interior. El itrio ayuda a bloquear la difusión de los elementos del sustrato (acero) para contenidos inferiores al (5 % at.) mejorando la funcionalidad protectora a alta temperatura de este tipo de recubrimientos

Corrosion preserving high density plasma treatment of precipitation hardening stainless steel

Specialty alloys such as precipitation hardening stainless steels are routinely used in critical applications requiring high strength and corrosion resistance, e.g. in aeronautics, in ground transportation and the biomedical field. Nonetheless, their tribological properties remain poor, while the application of surface treatments results in loss of corrosion resistance. Therefore, typically a not fully satisfactory compromise must be adopted. In the present work, the improvement of tribological features, without loss of corrosion resistance, of the 1.4545 (15-5PH) steel has been explored with the use of high density plasmas. The work has focused on long cylindrical geometries, close to those of real applications. The microstructure and composition of the treated surfaces were studied and the corresponding corrosion resistance stablished. The characteristics of the high density plasmas as well as the sample disposition were key factors in the outcomes, which ranged from fully corroded to corrosion resistant surfaces. Results also showed in certain cases the high density plasmas causing surface cracks followed by local corrosion. Additionally tribological studies demonstrated improvement in wear resistance, and electrical contact resistance (ECR) was found to be a good indicator of the wear phenomena occurring along the tests. An equivalent electric circuit is proposed. Actually ECR could be a useful and simple way of monitoring the surface status and assist in assuring safe and dependable operational lives of the components. In conclusion, treatment conditions of cylindrical 1.4545 (15-5PH) have been defined, which provide with an improved tribological performance, preserving corrosion resistance, with ECR a useful performance monitoring parameter.This work was supported the ProSurface project by MINECO (Spanish Ministry of Economy and Competitiveness) under grant No. RTC-2015-3595-4 and by the Economic Development Department at the Basque Government under Elkartek nG-17 grant

A general perspective of the characterization and quantification of nanoparticles: Imaging, spectroscopic, and separation techniques

This article gives an overview of the different techniques used to identify, characterize, and quantify engineered nanoparticles (ENPs). The state-of-the-art of the field is summarized, and the different characterization techniques have been grouped according to the information they can provide. In addition, some selected applications are highlighted for each technique. The classification of the techniques has been carried out according to the main physical and chemical properties of the nanoparticles such as morphology, size, polydispersity characteristics, structural information, and elemental composition. Microscopy techniques including optical, electron and X-ray microscopy, and separation techniques with and without hyphenated detection systems are discussed. For each of these groups, a brief description of the techniques, specific features, and concepts, as well as several examples, are described.Junta de Andalucía FQM-5974CEI-Biotic Granada CEI2013- MP-1

Solid lubricant behavior of MoS2 and WSe2-based nanocomposite coatings

Tribological coatings made of MoS2 and WSe2 phases and their corresponding combinations with tungsten carbide (WC) were prepared by non-reactive magnetron sputtering of individual targets of similar composition. A comparative tribological analysis of these multiphase coatings was done in both ambient air (30–40% relative humidity, RH) and dry nitrogen (RH<7%) environments using the same tribometer and testing conditions. A nanostructural study using advanced transmission electron microscopy of the initial coatings and examination of the counterfaces after the friction test using different analytical tools helped to elucidate what governs the tribological behavior for each type of environment. This allowed conclusions to be made about the influence of the coating microstructure and composition on the tribological response. The best performance obtained with a WSex film (specific wear rate of 2 × 10−8 mm3 N–1m–1 and a friction coefficient of 0.03–0.05) was compared with that of the well-established MoS2 lubricant material.The Spanish Ministry of Economy, Industry and Competitiveness [projects n° MAT2010-21597-C02-01, MAT2011-29074-C02-01; MAT2015-65539-P; MAT2015-69035-REDC], Junta de Andalucía [P10-TEP-67182] and Spanish National Research Council (CSIC) [201560E013] are acknowledged for their financial support

Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio

Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good

Juxtaposing BTE and ATE – on the role of the European insurance industry in funding civil litigation

One of the ways in which legal services are financed, and indeed shaped, is through private insurance arrangement. Two contrasting types of legal expenses insurance contracts (LEI) seem to dominate in Europe: before the event (BTE) and after the event (ATE) legal expenses insurance. Notwithstanding institutional differences between different legal systems, BTE and ATE insurance arrangements may be instrumental if government policy is geared towards strengthening a market-oriented system of financing access to justice for individuals and business. At the same time, emphasizing the role of a private industry as a keeper of the gates to justice raises issues of accountability and transparency, not readily reconcilable with demands of competition. Moreover, multiple actors (clients, lawyers, courts, insurers) are involved, causing behavioural dynamics which are not easily predicted or influenced. Against this background, this paper looks into BTE and ATE arrangements by analysing the particularities of BTE and ATE arrangements currently available in some European jurisdictions and by painting a picture of their respective markets and legal contexts. This allows for some reflection on the performance of BTE and ATE providers as both financiers and keepers. Two issues emerge from the analysis that are worthy of some further reflection. Firstly, there is the problematic long-term sustainability of some ATE products. Secondly, the challenges faced by policymakers that would like to nudge consumers into voluntarily taking out BTE LEI

Search for stop and higgsino production using diphoton Higgs boson decays

Results are presented of a search for a "natural" supersymmetry scenario with gauge mediated symmetry breaking. It is assumed that only the supersymmetric partners of the top-quark (stop) and the Higgs boson (higgsino) are accessible. Events are examined in which there are two photons forming a Higgs boson candidate, and at least two b-quark jets. In 19.7 inverse femtobarns of proton-proton collision data at sqrt(s) = 8 TeV, recorded in the CMS experiment, no evidence of a signal is found and lower limits at the 95% confidence level are set, excluding the stop mass below 360 to 410 GeV, depending on the higgsino mass

Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon

The current consensus is that drought has developed in the Sahel during the second half of the twentieth century as a result of remote effects of oceanic anomalies amplified by local land–atmosphere interactions. This paper focuses on the impacts of oceanic anomalies upon West African climate and specifically aims to identify those from SST anomalies in the Pacific/Indian Oceans during spring and summer seasons, when they were significant. Idealized sensitivity experiments are performed with four atmospheric general circulation models (AGCMs). The prescribed SST patterns used in the AGCMs are based on the leading mode of covariability between SST anomalies over the Pacific/Indian Oceans and summer rainfall over West Africa. The results show that such oceanic anomalies in the Pacific/Indian Ocean lead to a northward shift of an anomalous dry belt from the Gulf of Guinea to the Sahel as the season advances. In the Sahel, the magnitude of rainfall anomalies is comparable to that obtained by other authors using SST anomalies confined to the proximity of the Atlantic Ocean. The mechanism connecting the Pacific/Indian SST anomalies with West African rainfall has a strong seasonal cycle. In spring (May and June), anomalous subsidence develops over both the Maritime Continent and the equatorial Atlantic in response to the enhanced equatorial heating. Precipitation increases over continental West Africa in association with stronger zonal convergence of moisture. In addition, precipitation decreases over the Gulf of Guinea. During the monsoon peak (July and August), the SST anomalies move westward over the equatorial Pacific and the two regions where subsidence occurred earlier in the seasons merge over West Africa. The monsoon weakens and rainfall decreases over the Sahel, especially in August.Peer reviewe

Search for anomalous production of events with three or more leptons in pp collisions at √s = 8TeV

Published by the American Physical Society under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published articles title, journal citation, and DOI.A search for physics beyond the standard model in events with at least three leptons is presented. The data sample, corresponding to an integrated luminosity of 19.5fb-1 of proton-proton collisions with center-of-mass energy s=8TeV, was collected by the CMS experiment at the LHC during 2012. The data are divided into exclusive categories based on the number of leptons and their flavor, the presence or absence of an opposite-sign, same-flavor lepton pair (OSSF), the invariant mass of the OSSF pair, the presence or absence of a tagged bottom-quark jet, the number of identified hadronically decaying τ leptons, and the magnitude of the missing transverse energy and of the scalar sum of jet transverse momenta. The numbers of observed events are found to be consistent with the expected numbers from standard model processes, and limits are placed on new-physics scenarios that yield multilepton final states. In particular, scenarios that predict Higgs boson production in the context of supersymmetric decay chains are examined. We also place a 95% confidence level upper limit of 1.3% on the branching fraction for the decay of a top quark to a charm quark and a Higgs boson (t→cH), which translates to a bound on the left- and right-handed top-charm flavor-violating Higgs Yukawa couplings, λtcH and λctH, respectively, of |λtcH|2+|λctH|2<0.21