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Mn-rich Ni–Mn–Sn metamagnetic shape memory alloys exhibiting magnetostructural transformation are of a great potential as the base materials for solid-state refrigeration. With the aim of fine tuning of the transformation characteristics and improving functional properties, in the present work we have fabricated polycrystalline Ni50-xFexMn40Sn10 (x = 0, 2, 4, 6, 8 at.%) melt-spun ribbons, starting from the base alloy with x = 0, which is weakly magnetic in both austenitic and martensitic phases. By exploring martensitic transformation (MT) and magnetic behaviors as a function of Fe doping and magnetic field, we have found that Fe and/or magnetic field reduce the MT temperature and Curie temperature of austenite phase, becoming closer to each other as the Fe-content increases, accompanied by an increase of the magnetic moment of austenite, magnetization jump at MT, transformation volume, and magnetic contribution, ΔSM, to the total entropy change at MT. The ribbons present moderate values of ΔSM equal to 11 J kg−1K−1 at 5 T for x = 8, moderate thermal hysteresis (10–14 K) nearly independent of Fe doping or magnetic field, and adjustable structural and magnetic transition temperatures close to room temperature.

A kinetic study of the CO2 desorption process by carbonated sodium zirconate (Na2ZrO3) synthesized by a liquid suspension route is presented using zirconium acetylacetonate and sodium acetate as precursors. Na2ZrO3 was characterized by XRD, SEM and TGA. Na2ZrO3 exhibited a 90% conversion during absorption with respect to the theoretical value. CO2 desorption kinetic study used three temperatures; 850, 900 °C and 950 °C and three concentrations: 5, 3 and 1% of CO2 in Ar at 200 ml/min. XRD data shown only slight segregation of the precursors, which led to a small amount of ZrO2 formation in the solid product. The global rate of the decarbonation reaction of Na2ZrO3 was of first order in CO2 concentration and strongly dependent on temperature. The calculated apparent activation energy was EA = 23.35 kcal/mol. Na2ZrO3 performance during four continuous cycles, shown an excellent thermal and chemical stability, with the material conversion remaining practically unchanged.

Microstructure, martensitic transformation temperatures, hardness, and magnetic properties have been studied in Co–Ni–Ga alloys for different compositions of Co and Ni. Hardness, transformation temperatures and thermal hysteresis show a decrease with Co content. On the contrary, maximal magnetization, and magnetic hysteresis both grow with cobalt composition.

Some thermal and structural characteristics of Ni–Fe–Ga alloys were studied by means of differential scanning calorimetry (DSC), thermo mechanical analysis (TMA), and X-ray diffraction techniques. It was observed that martensitic transition temperature rapidly decreases and Curie temperature increases with Fe content. The order–disorder transition temperature from a L21 to A2 structures grows linearly with iron content, as measured by TMA. TMA has been found as a useful tool to perform these characterizations.

Trabajo fin de grado. Defendido el 22 de enero de 2015. Bibliografía: p. 65-67 (Según el contador de la aplicación) : Carpeta 1-4: Curriculum vitae ; Resume informativo ; Resumen indicativo ; TFG Este trabajo trata de analizar la casuística específica que se da en la Institución de la Responsabilidad Patrimonial en el ámbito de la Sanidad Publica en España, descubriendo que existen una serie de casos, que por su repetición podemos calificar como de típicos en materia de Responsabilidad Patrimonial Sanitaria. La falta o deficiencia en el consentimiento informado, la obligación de proporcionar los medios adecuados, la diferenciación entre medicina curativa y satisfactoria, la teoría del daño desproporcionado, la pérdida de oportunidad o los casos de infección nosocomial se convierten en típicos por su reiteración en la práctica cotidiana de la medicina en los hospitales de nuestro país. Abstract: This paper attempts to analyze the specific case occurring in the institution of the Patrimonial Responsibility in the field of Public Health in Spain, discovering that a series of cases that repetition can qualify as typical in Health Equity Responsibility. The lack or deficiency in the informed consent, the obligation to provide adequate means, the differentiation between curative and satisfactiva medicine, theory disproportionate harm, the loss of opportunity or cases of nosocomial infection become typical for its repetition in everyday practice of medicine in hospitals in our country. Ordenador con navegador de Internet ; Adobe Acrobat Reader 67 p. (Según el contador de la aplicación)

Acoustic emission has been measured and statistical characteristics analyzed during the stress-induced collapse of porous berlinite, AlPO4, containing up to 50 vol% porosity. Stress collapse occurs in a series of individual events (avalanches), and each avalanche leads to a jerk in sample compression with corresponding acoustic emission (AE) signals. The distribution of AE avalanche energies can be approximately described by a power law p(E)dE = E(-ε)dE (ε ~ 1.8) over a large stress interval. We observed several collapse mechanisms whereby less porous minerals show the superposition of independent jerks, which were not related to the major collapse at the failure stress. In highly porous berlinite (40% and 50%) an increase of energy emission occurred near the failure point. In contrast, the less porous samples did not show such an increase in energy emission. Instead, in the near vicinity of the main failure point they showed a reduction in the energy exponent to ~ 1.4, which is consistent with the value reported for compressed porous systems displaying critical behavior. This suggests that a critical avalanche regime with a lack of precursor events occurs. In this case, all preceding large events were 'false alarms' and unrelated to the main failure event. Our results identify a method to use pico-seismicity detection of foreshocks to warn of mine collapse before the main failure (the collapse) occurs, which can be applied to highly porous materials only.

The failure dynamics in SiO(2)-based porous materials under compression, namely the synthetic glass Gelsil and three natural sandstones, has been studied for slowly increasing compressive uniaxial stress with rates between 0.2 and 2.8 kPa/s. The measured collapsed dynamics is similar to Vycor, which is another synthetic porous SiO(2) glass similar to Gelsil but with a different porous mesostructure. Compression occurs by jerks of strain release and a major collapse at the failure point. The acoustic emission and shrinking of the samples during jerks are measured and analyzed. The energy of acoustic emission events, its duration, and waiting times between events show that the failure process follows avalanche criticality with power law statistics over ca. 4 decades with a power law exponent ɛ≃ 1.4 for the energy distribution. This exponent is consistent with the mean-field value for the collapse of granular media. Besides the absence of length, energy, and time scales, we demonstrate the existence of aftershock correlations during the failure process.

We study the acoustic emission avalanches during the failure process of porous alumina samples (Al2O3) under compression. Specimens with different porosities ranging from 30% to 59% have been synthetized from a mixture of fine-grained alumina and graphite. The compressive strength as well as the characteristics of the acoustic activity have been determined. The statistical analysis of the recorded acoustic emission pulses reveals, for all porosities, a broad distribution of energies with a fat tail, compatible with the existence of an underlying critical point. In the region of 35%-55% porosity, the energy distributions of the acoustic emission signals are compatible with a power law behavior over two decades in energy with an exponent \epsilon = 1.8+/-0.1., Comment: 16 pages, 13 figures, Submitted to: Journal of Physics: Condensed Matter

We have studied magnetocaloric properties of a Ni-Mn-In metamagnetic shape-memory alloy especially designed in order to display low thermal hysteresis. Magnetization and calorimetric measurements under a magnetic field have been used in order to determine isothermal magnetic field-induced entropy changes. Results obtained indirectly from magnetization data, quasi-directly from isofield calorimetric measurements, and directly from isothermal calorimetric runs are systematic and agree well with each other. We have analyzed the reproducibility of magnetocaloric properties with cycling from direct isothermal calorimetric measurements. Due to low thermal hysteresis, we have found that about 80% of the transition entropy change, ΔSt ≃ 25 J/kg K, can be reversibly induced under successive application and removal of a field of 6 T.

We have studied magnetocaloric and elastocaloric properties of a Ni-Mn-Sn(Cu) metamagnetic shape-memory alloy undergoing a magneto-structural transition (martensitic type) close to room temperature. Changes of entropy have been induced by isothermally applying both mechanical (uniaxial stress) and magnetic fields. These entropy changes have been, respectively, estimated from dilatometric measurements giving the length of the sample as a function of temperature at selected applied forces and magnetic fields and from magnetization measurements as a function of temperature at selected applied magnetic fields. Our results indicate that the elastocaloric effect is conventional and occurs in two steps which reflect the interplay between the martensitic and the incipient magnetic transitions. By contrast, the magnetocaloric effect is inverse and occurs in a single step that encompasses the effect arising from both transitions.