Stratigraphy, structure and geodynamic evolution of the Paleozoic rocks in the Cordillera del Viento (37º S latitude, Andes of Neuquén, Argentina)

The Pre-Andean Paleozoic substrate from the Cordillera del Viento anticline is a polyorogenic basement composed of two groups of preorogenic rocks with different stratigraphy and deformation. The oldest set consists of pre-Late Devonian metasedimentary rocks belong­ing to the Guaraco Norte Formation. The upper set is formed by the thick volcano-sedimentary sequence of the Carboniferous Andacollo Group. This group is composed from bottom to top of the silicic volcanic rocks of the Arroyo del Torreón Formation (early Carboniferous) and the marine sedimentary rocks of the Huaraco Formation (late Carboniferous) developed in an extensional basin. Both formations are locally separated by minor syn-extensional unconformities. The relationship between the metamorphic rocks of the Guaraco Norte Formation and the volcano-sedimentary sequence of the Anda­collo Group is not observed, but we inferred a major angular unconformity associated with the Late Devonian-early Carboniferous Chanic orogeny. The main Chanic structures are tight vertical and subvertical folds with slight W-WSW vergence, formed under low-grade meta­morphic conditions, with the development of a pervasive axial-plane cleavage (S1), affected by a disjunctive crenulation cleavage (S2). In the early Permian, during the San Rafael orogeny of the Gondwanan orogenic cycle, deformation occurred under very low-grade to non-metamorphic conditions. The main structures are thrusts and associated folds that are re-folded by the Cordillera del Viento anticline, related to the Andean orogeny. The WNW-oriented and SSW-vergent folds are associated with an incipient axial-plane cleavage in the pyroclastic rocks and pencil lineation in shales. The pre-Andean Paleozoic basement rocks are intruded and unconformably covered by early Permian to Early Triassic? granitoids and silicic volcanic rocks from the Huingancó volcanic-plutonic Complex (equivalent to the Choiyoi Group), establishing the beginning of the Andean orogenic cycle in this region.El sustrato paleozoico pre-andino que aflora en el anticlinal de la Cordillera del Viento, es un basamento poliorogénico que está com­puesto por dos conjuntos de rocas preorogénicas con estratigrafía y condiciones de deformación diferentes. El más antiguo tiene una edad devónica superior y está formado por las rocas metasedimentarias de la Formación Guaraco Norte, en tanto que el conjunto superior son las espesas acumulaciones volcano-sedimentarias carboníferas del Grupo Andacollo. Este grupo, integrado en su parte inferior por rocas volcánicas silíceas de la Formación Arroyo del Torreón (Carbonífero inferior) y hacia techo, por las sedimentitas clásticas marinas de la Formación Huaraco (Carbonífero superior) fue desarrollado en el marco de una cuenca extensional y pueden estar separadas localmente por discordancias menores de carácter sin-extensional. Las relaciones entre las rocas metamórficas y la secuencia volcano-sedimentaria del Carbonífero no se observan, pero se infiere una discordancia mayor asociada con la orogenia Chánica, que tuvo lugar entre el Devónico Superior y el Carbonífero inferior. Las estructuras chánicas están asociadas a un metamorfismo de bajo grado y son pliegues apretados sub-verticales a verticales y con ligera vergencia al O-OSO que llevan asociados un clivaje penetrativo (S1) de rumbo N-S a NNO que está afectado por un clivaje subvertical más espaciado (S2). En el Pérmico inferior, durante la orogenia San Rafael del ciclo orogénico Gondwánico, la deformación contraccional se produce en condiciones de metamorfismo de muy bajo grado o en ausencia de éste. Las estructuras principales son cabalgamientos y pliegues asociados que se encuentran plegados por el anticlinal ándico de la Cordillera del Viento. Los pliegues de rumbo ONO y vergencia al SSO llevan asociados un incipiente clivaje de plano axial en los contactos entre limolitas y volcanitas y lineación de tipo lápiz (pencil) en las lutitas. Las rocas del basamento paleozoico pre-ándico están intruidas y cubiertas discordantemente por rocas volcánicas silíceas de edad Pér­mico inferior a Triásico Inferior?, correspondientes al Complejo volcánico-plutónico Huingancó (equivalente al Grupo Choiyoi), unidad que marca el comienzo el ciclo orogénico Andino, en esta región

Low temperature degradation behaviour of 10Ce-TZP/Al2O3 bioceramics obtained by microwave sintering technology

Zirconia is one of the most used ceramics, especially for biomedical applications, due to its exceptional mechanical properties. However, it is commonly known that its properties can be diminished owing to a low temperature degradation (LTD). This phenomenon consists on a spontaneous phase transformation, from tetragonal to monoclinic, under certain conditions, which is accelerated when the samples are exposed under high levels of humidity at a temperature range between 20-300 ºC. In addition to the fact that the monoclinic phase presents worse mechanical properties than the tetragonal one, there is a volume change of 4% between phases that gives rise to defects in the material as microcracks. Due to this reason, zirconia prostheses failed catastrophically inside the human body between 1999 and 2001 (1). Previous researches reveal that Al2O3 addition suppress the propagation of phase transformation (2). Thus, the aim of the present work is to study the hydrothermal ageing of zirconia doped with ceria and toughened with alumina (10Ce-TZP/Al2O3) composite, which has been sintered by microwave employing two different frequencies: 2.45 and 5.8 GHz. Microwave heating technology is based on the absorption of electromagnetic radiation by the material, which allows the sample to be heated. So far, most microwave heating equipments use 2.45 GHz; accordingly, the novelty of this study is to employ a frequency of 5.8 GHz and to investigate its effect on LTD. LTD is carried out in an autoclaved in steam at 120 ºC and 1.2 bar, because these conditions accelerate the hydrothermal aging process (3). In order to characterize the degraded samples, micro-Raman spectroscopy, AFM, nanoindentation technique and electronic microscopy have been performed. References 1. Norton, M. R., Yarlagadda, R., Anderson, G. H. J. Bone Joint Surg. Br., 2002, 84–B, 631–635. 2. Fabbri, P., Piconi, C., Burresi, E., Magnani, G., Mazzanti, F., Mingazzini, C. Dent. Mater., 2014. 3. Presenda, Á., Salvador, M. D., Moreno, R., Borrell, A. J. Am. Ceram. Soc., 2015, 98, 3680–3689

Análisis cinetoestático de un mecanismo articulado y un engranaje no circular cinemáticamente equivalentes

En multitud de aplicaciones es de interés diseñar mecanismos con relación de transmisión variable a lo largo de una vuelta del eslabón conductor. Ésta se puede obtener con diferentes mecanismos, entre ellos los engranajes no circulares. En este trabajo se comparan la fluctuación del par motor y la fuerza transmitida al chasis en un engranaje no circular y en un mecanismo articulado con igual ley de desplazamiento y bajo similares condiciones de operación

Estudio sobre las leyes de desplazamiento en los engranajes no circulares

En este artículo se realiza un estudio sobre las propiedades requeridas por algunas funciones (curvas de Bézier, B-spline, cicloidal) cuando se utilizan como leyes de desplazamiento de dos ruedas no circulares. Se realiza el estudio de la función requerida para obtener una rueda elíptica. Se considera el caso donde las ruedas conductora y conducida tienen diferentes periodos

Numerical analysis of microwave heating cavity: Combining electromagnetic energy, heat transfer and fluid dynamics for a NaY zeolite fixed-bed

[EN] Three-dimensional mathematical model was developed for a rectangular TE10n microwave heating cavity system, working at 2.45 GHz. Energy/heat, momentum equations were solved together with Maxwell's electromagnetic field equations using comm. MULTIPHYSICS (R) simulation environment. The dielectric properties, epsilon' and epsilon '', of NaY zeolite (Si/Al = 2.5) were evaluated as a function of temperature. Considering these values, the microwave heating of a porous fixed-bed made of dry NaY zeolite was simulated. Electric field distribution, axial and radial temperature profiles and temperature evolution with time were obtained. The zeolite fixed bed was heated up to 180 degrees C in 5 min, with 30 W power. The fixed-bed temperature evolution under non-steady state conditions showed the same trend as the one observed experimentally with only an average deviation of 10.3%. The model was used to predict microwave heating of other materials improving energy efficiency of the microwave cavity. Furthermore, the developed model was able to predict thermal runaway for zeolites.Financial support from the European Research Council ERC-Advanced Grant HECTOR-267626 is gratefully acknowledged. Hakan Nigar acknowledges financial support from the Spanish Ministry of Education for the FPU grant (Formacion del Profesorado Universitario - FPU12/06864), and also for the academic short stay grant (Estancia Breve - FPU2016) at the Delft University of Technology, Delft, The Netherlands.Nigar, H.; Sturm, GSJ.; García-Baños, B.; Penaranda-Foix, FL.; Catalá Civera, JM.; Mallada, R.; Stankiewicz, A.... (2019). Numerical analysis of microwave heating cavity: Combining electromagnetic energy, heat transfer and fluid dynamics for a NaY zeolite fixed-bed. Applied Thermal Engineering. 155:226-238. https://doi.org/10.1016/j.applthermaleng.2019.03.117S22623815

Comparison in mechanical properties of zirconium titanate (ZrTiO4) synthetized by alternative routes and sintered by microwave (MW)

[EN] At present, ZrTiO4 nanopowders are used as a dielectric in the electroceramic field, applications of catalysis, microwave telecommunications devices, pigments, composites, etc. One of the most interesting applications is the potential as structural material and similar applications that require a high thermal resistance. However, all the properties of zirconium titanate are still a subject of interest for the industrial field.12 There are several routes of synthesis of ZrTiO4; among them is the sol-gel method and lyophilization. These methods have been used to make powders or small pieces of zirconium titanate. However, structural applications require materials in large quantities, so it is necessary to identify the differences between the methods of synthesizing and allowing the preparation of powders suitable for the generation of green materials for subsequent sintering.3 To develop a new generation of nanomaterials with microstructural differences it is necessary to innovate in the sintering process. Years ago, the use of conventional oven for sintering material was the usual procedure. Nowadays, non-conventional methods as Microwave sintering (MW) are a bright way to produce high dense materials, using heating rates in reduce dwell times and lower consumption using 70%-80% less energy. 4 This reactive sintering technique achieves excellent mechanical properties, homogeneous microstructure employing lower sintering temperatures. All these energy and economic advantages generate a new vision for the future on ceramic materials and their industrial production. The main objective of this study is to make a comparison of the mechanical properties of the materials synthesized by sol-gel method and lyophilization and sintered by microwaves.The authors would like to thank to the Generalitat Valenciana for financial support received for Santiago Grisolía program scholarship (GRISOLIAP/2018/168). A. Borrell acknowledges the Spanish Ministry of Economy and Competitiveness for her RyC contract (RYC-2016-20915).Guillén Pineda, RM.; Borrell Tomás, MA.; Salvador Moya, MD.; Peñaranda Foix, FL.; Moreno, R. (2019). Comparison in mechanical properties of zirconium titanate (ZrTiO4) synthetized by alternative routes and sintered by microwave (MW). En AMPERE 2019. 17th International Conference on Microwave and High Frequency Heating. Editorial Universitat Politècnica de València. 433-438. https://doi.org/10.4995/AMPERE2019.2019.9892OCS43343