Surface modification of Al2O3–ZrO2(Y2O3) eutectic oxides by laser melting: processing and wear resistance

Surface coatings of pseudo-binary Al2O3–Zr2O3(Y2O3) eutectic oxides were produced by laser melting of the surface of conventionally sintered materials using a high-power diode laser. It was possible to obtain smooth, homogeneous, and crack-free coatings up to 50_7 mm2 in area by carefully controlling the processing conditions (laser power, traveling speed of the specimen, and substrate temperature). The surface treatment was aimed at creating a dense, wear-resistant coating based on the eutectic microstructure generated upon solidification. The microstructure of the coating was formed by elongated colonies, and was similar to that found in rods grown by the laser-heated floating zone method at the same growth rates. The laser-melted coating presented much higher hardness and wear resistance than the sintered materials, and the optimum mechanical properties were measured in samples treated at 500 mm/h with a laser line power of 65–80 W/cm. These samples presented a hardness and wear rate of 19.770.4 GPa and 3.8_10_6 mm3/N m, respectively, while those of the conventionally sintered materials were 14.37 0.2 GPa and 2.3_10_6 mm3/N m

Micropillar compression of LiF [111] single crystals: effect of size, ion irradiation and misorientation

The mechanical response under compression of LiF single crystal micropillars oriented in the [111] direction was studied. Micropillars of different diameter (in the range 1–5 lm) were obtained by etching the matrix in directionally-solidified NaCl–LiF and KCl–LiF eutectic compounds. Selected micropillars were exposed to high-energy Ga+ ions to ascertain the effect of ion irradiation on the mechanical response. Ion irradiation led to an increase of approximately 30% in the yield strength and the maximum compressive strength but no effect of the micropillar diameter on flow stress was found in either the as-grown or the ion irradiated pillars. The dominant deformation micromechanisms were analyzed by means of crystal plasticity finite element simulations of the compression test, which explained the strong effect of micropillar misorientation on the mechanical response. Finally, the lack of size effect on the flow stress was discussed to the light of previous studies in LiF and other materials which show high lattice resistance to dislocation motion

Interacting plasmon and phonon polaritons in aligned nano- and microwires

The availability of macroscopic, nearly periodic structures known as eutectics opens a new path for controlling light at wavelength scales determined by the geometrical parameters of these materials and the intrinsic properties of their component phases. Here, we analyze the optical waveguiding properties of eutectic mixtures of alkali halides, formed by close-packed arrangements of aligned cylindrical inclusions. The wavelengths of phonon polaritons in these constituents are conveniently situated in the infrared and are slightly larger than the diameter and separation of the inclusions, typically consisting on single-crystal wires down to submicrometer diameter. We first discuss the gap mode and the guiding properties of metallic cylindrical waveguides in the visible and near-infrared, and in particular we investigate the transition between cylinder touching and non-touching regimes. Then, we demonstrate that these properties can be extended to the mid infrared by means of phonon polaritons. Finally, we analyze the guiding properties of an actual eutectic. For typical eutectic dimensions, we conclude that crosstalk between neighboring cylindrical wires is small, thus providing a promising platform for signal propagation and image analysis in the mid infrared

Self-organization approach for THz polaritonic metamaterials

In this paper we discuss the fabrication and the electromagnetic (EM) characterization of anisotropic eutectic metamaterials, consisting of cylindrical polaritonic LiF rods embedded in either KCl or NaCl polaritonic host. The fabrication was performed using the eutectics directional solidification self-organization approach. For the EM characterization the specular reflectance at far infrared, between 3 THz and 11 THz, was measured and also calculated by numerically solving Maxwell equations, obtaining good agreement between experimental and calculated spectra. Applying an effective medium approach to describe the response of our samples, we predicted a range of frequencies in which most of our systems behave as homogeneous anisotropic media with a hyperbolic dispersion relation, opening thus possibilities for using them in negative refractive index and imaging applications at THz range

Role of age and comorbidities in mortality of patients with infective endocarditis

Purpose: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. Methods: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015. Patients were stratified into three age groups:<65 years, 65 to 80 years, and = 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. Results: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 = 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients =80 years who underwent surgery were significantly lower compared with other age groups (14.3%, 65 years; 20.5%, 65-79 years; 31.3%, =80 years). In-hospital mortality was lower in the <65-year group (20.3%, <65 years;30.1%, 65-79 years;34.7%, =80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%, =80 years; p = 0.003).Independent predictors of mortality were age = 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI = 3 (HR:1.62; 95% CI:1.39–1.88), and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared, the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. Conclusion: There were no differences in the clinical presentation of IE between the groups. Age = 80 years, high comorbidity (measured by CCI), and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

A Luminescent Pt3Pb cluster with three Pt(II)®Pb(II) bonds

The reaction between the pentafluorophenylplatinate derivative Pb(ClO4)2 (1.5:1) in dry tetrahydrofuran yields the tetranuclear complex (NBu4)[Pb{Pt(-Cl) (C6F5)2}3] (1). The crystal structure of this compound has been analyzed by X-ray diffraction and reveals the presence of three PtPb metal-metal bonds. This complex shows luminescence at low temperature. © 2002 Elsevier Science B.V. All rights reserved

Laser processing of ceramic materials for electrochemical and high temperature energy applications

The laser is a powerful tool for materials processing, incorporated already in many industrial processes and laboratory procedures. In this work, we are concerned with laser processing applied to research and development of ceramics for electrochemical cells and other high temperature oxide ceramics for energy applications. Solidification of single crystals or composites of relevant oxides can be performed by the laser assisted floating zone method, providing samples for structural, mechanical or functional fundamental research, as well as knowledge about its manufacture by melt processes. Selective laser melting of these ceramic oxides is a very promising technology, at the research level. Successful examples of surface laser melting of oxide eutectic composites are presented. The technologies of subtractive laser processing of ceramics (cutting, drilling, structuring, cleaning, etc.) are more developed, and the research is directed towards the optimization of mechanisms, increase of resolution and efficiency and the investigation of the effects of the laser treatment on the functional performance. Different laser processes of SOC (solid oxide cell) components are shown to decrease the ohmic, concentration and activation losses. The manuscript describes the state-of-the art of the technologies as applied to oxide and composite materials present in solid oxide electrochemical devices (SOFC, SOEC, and batteries) and selective emitters for thermophotovoltaics, with emphasis on the last achievements by the authors team. El láser es una potente herramienta para el procesamiento de materiales, incorporada ya en muchos procesos industriales y procedimientos de laboratorio. En este trabajo nos ocupamos del procesamiento láser aplicado a la investigación y desarrollo de cerámicas para celdas electroquímicas y otras cerámicas de óxido de alta temperatura para aplicaciones energéticas. La solidificación de monocristales o composites de óxidos relevantes se puede realizar mediante el método de zona flotante asistida por láser, proporcionando muestras para investigación básica estructural, de propiedades mecánicas o funcionales, así como conocimiento sobre su fabricación mediante procesos de fusión. La fusión selectiva por láser de estos óxidos cerámicos es una tecnología muy prometedora, cuyo desarrollo es todavía incipiente. Se presentan ejemplos exitosos de fusión por láser de superficie de compuestos eutécticos de óxidos. Las tecnologías sustractivas de procesamiento de cerámicas con láser (corte, taladrado, estructuración, limpieza, etc.) están más desarrolladas, y la investigación se dirige hacia la optimización de procedimientos, aumento de resolución y eficiencia y la investigación de los efectos del tratamiento láser sobre el rendimiento funcional. Diferentes procesos láser de los componentes de celda de óxido sólido disminuyen las pérdidas óhmicas, de concentración y de activación. El manuscrito describe el estado actual de las tecnologías aplicadas a óxidos y materiales compuestos presentes en dispositivos electroquímicos de óxidos sólidos (SOFC, SOEC y baterías) y emisores selectivos para aplicaciones termofotovoltaicas, con énfasis en los últimos logros del equipo

Structured YBa2Cu3O7-δ thin films grown on aligned calcium stabilized zirconia-calcium zirconate lamellar eutectic substrates

In this paper we present a new approach to obtain structured biepitaxial films by using eutectic substrates. In particular we have deposited YBa2Cu3O7-δ (YBCO) thin films grown by Metal-Organic Chemical Vapor Deposition (MOCVD) on eutectic Ca-stabilized Zirconia - CaZrO3 (CSZ-CZO) substrates structured in the form of parallel lamellae. The films reproduce the pattern of the substrate and show ordered arrays of alternating c-axis and (103)-oriented YBCO strips. Crystallographic characterisation reveals that YBCO films grow epitaxially on both eutectic phases. The structured films were analysed by EPMA, and micro-Raman. The films show anisotropic transport properties in both normal (resistivity anisotropy ρT/ρL (300K) ≈ 1.9) and superconducting states (critical current anisotropy at 77K JcL/JcT ≈ 13) when measured along (L) or transverse (T) to the substrate lamellae. Transport along transverse direction showed a considerably higher sensitivity to applied magnetic field than measurements in the longitudinal direction. This was attributed to the weak-link behaviour of the artificially-induced grain boundaries between strips