Thermal Stability of Cu-Al-Ni Shape Memory Alloy Thin Films Obtained by Nanometer Multilayer Deposition

Cu-Al-Ni is a high-temperature shape memory alloy (HTSMA) with exceptional thermomechanical properties, making it an ideal active material for engineering new technologies able to operate at temperatures up to 200 °C. Recent studies revealed that these alloys exhibit a robust superelastic behavior at the nanometer scale, making them excellent candidates for developing a new generation of micro-/nano-electromechanical systems (MEMS/NEMS). The very large-scale integration (VLSI) technologies used in microelectronics are based on thin films. In the present work, 1 μm thickness thin films of 84.1Cu-12.4 Al-3.5Ni (wt.%) were obtained by solid-state diffusion from a multilayer system deposited on SiNx (200 nm)/Si substrates by e-beam evaporation. With the aim of evaluating the thermal stability of such HTSMA thin films, heating experiments were performed in situ inside the transmission electron microscope to identify the temperature at which the material was decomposed by precipitation. Their microstructure, compositional analysis, and phase identification were characterized by scanning and transmission electron microscopy equipped with energy dispersive X-ray spectrometers. The nucleation and growth of two stable phases, Cu-Al-rich alpha phase and Ni-Al-rich intermetallic, were identified during in situ heating TEM experiments between 280 and 450 °C. These findings show that the used production method produces an HTSMA with high thermal stability and paves the road for developing high-temperature MEMS/NEMS using shape memory and superelastic technologies.This research was funded by the Spanish Ministry of Science and Innovation, project PID2021-122160NB-I00, and the GIU-21/024 from the University of the Basque Country, UPV/EHU. This work made use of the TEM and SEM facilities of the Electron Microscopy and Microanalysis of Materials SGIKER of the UPV/EHU, as well as the FIB facilities of EML at NanoGune

Twitter as a Strategic Tool in Ecuadorian Politics

La revuelta policial del 30S en el 2011 en Ecuador visibilizó a Twitter como medio de comunicación y coerción ideológica. Este artículo estudia el escenario político formado por 22 partidos políticos en Ecuador. Sólo 11 partidos políticos tienen Twitter, y esto determina la relación entre el número de seguidores y el éxito en las urnas. Los partidos con mayor número de seguidores en Twitter son más aceptados por el público. Pero también movimientos políticos “veteranos” se mantienen en el plano político con una presencia mínima o sin usar herramientas Web 2.0.30S police revolt in Ecuador in 2011 made visible to Twitter as a communication and ideological coercion. This article examines the political arena formed by 22 political parties in Ecuador. Only 11 political parties have Twitter, and this determines the ratio of the number of fans and the success at the polls. The party with the largest number of followers on Twitter are more accepted by the public. But political movements "veterans" remain at the political level with or without tools Web 2.0 a minimal presence

The Influence of Thermal History on the Multistage Transformation of NiTi Shape-Memory Alloys

The multistage martensitic phase transformation of a polycrystalline NiTi shape-memory alloy (50.3 at. %Ni-49.7 at. % Ti) has been studied by means of calorimetric measurements. After a conventional thermal treatment followed by successive thermal cycles, the initial two-step forward transformation splits into four-overlapping stages. However, the reverse martensitic transformation maintains the initial two-step sequence, usually assigned to the B19'-> R -> B2 transformation. The correlation between the forward and reverse steps has been established by means of selected thermal cycles together with an estimation of their enthalpy and thermal hysteresis. These results have also provided information about the storage of the elastic strain energy and the frictional works associated with the variants' nucleation. Moreover, the study around the forward transformation temperature range by means of uncompleted thermal cycles undoubtedly shows the presence of temperature memory effects in both stages.This work has been supported by the Spanish Ministry of Economy and Competitiveness, MINECO, CONSOLIDER-INGENIO 2010 CSD2009-00013, as well as by the Consolidated Research Group IT-1090-16 and the ELKARTEK-ACTIMAT project from the Education and Industry Departments of the Basque Government. The University of the Basque Country has also supported this work with the Research Group grant: UPV/EHU GIU17/071. The authors appreciate the cooperation of J. Rodriguez-Aseguinolaza in the thermal treatments of the samples

Designing for Shape Memory in Additive Manufacturing of Cu–Al–Ni Shape Memory Alloy Processed by Laser Powder Bed Fusion

Shape memory alloys (SMAs) are functional materials that are being applied in practically all industries, from aerospace to biomedical sectors, and at present the scientific and technologic communities are looking to gain the advantages offered by the new processing technologies of additive manufacturing (AM). However, the use of AM to produce functional materials, like SMAs, constitutes a real challenge due to the particularly well controlled microstructure required to exhibit the functional property of shape memory. In the present work, the design of the complete AM processing route, from powder atomization to laser powder bed fusion for AM and hot isostatic pressing (HIP), is approached for Cu–Al–Ni SMAs. The microstructure of the different processing states is characterized in relationship with the processing parameters. The thermal martensitic transformation, responsible for the functional properties, is analyzed in a comparative way for each one of the different processed samples. The present results demonstrate that a final post–processing thermal treatment to control the microstructure is crucial to obtain the expected functional properties. Finally, it is demonstrated that using the designed processing route of laser powder bed fusion followed by a post–processing HIP and a final specific thermal treatment, a satisfactory shape memory behavior can be obtained in Cu–Al–Ni SMAs, paving the road for further applications.This research was supported by the Industry Department of the Basque Government through the ELKARTEK–CEMAP (KK–2020/00047) project, as well as from the GIU–17/071 from the University of the Basque Country UPV/EHU. Financial support was also received from the Spanish Ministry of Economy and Competitiveness, MINECO, through the project MAT2017-84069P. This work made use of the facilities from the Electronic Microscopy and Material Microanalysis Service of the SGIKER from the UPV/EHU. M.P.-C. acknowledges the pre–doctoral grant (PRE_2019_2_0268) from the Education Department of the Basque Country. J.F.G.-C. thanks the post–doctoral grant (ESPDOC18/37) from the UPV/EHU

Strain Relaxation in Cu-Al-Ni Shape Memory Alloys Studied by in Situ Neutron Diffraction Experiments

In situ neutron diffraction is used to study the strain relaxation on a single crystal and other powdered Cu-Al-Ni shape memory alloys (SMAs) around martensitic transformation temperatures. This work is focused on the analysis of the strain evolution along the temperature memory effect appearing in these alloys after partial thermal transformations. A careful study of the influence of partial cycling on the neutron diffraction spectra in the martensitic phase is presented. Two different effects are observed, the d-spacing position shift and the narrowing of various diffraction peaks, along uncompleted transformation cycles during the thermal reverse martensitic transformation. These changes are associated with the relaxation of the mechanical stresses elastically stored around the martensitic variants, due to the different self-accommodating conditions after uncompleted transformations. The evolution of the stresses is measured through the strain relaxation, which is accessible by neutron diffraction. The observed effects and the measured strain relaxations are in agreement with the predictions of the model proposed to explain this behavior in previous calorimetric studies. In addition, the thermal expansion coefficients of both martensite and austenite phases were measured. The neutron experiments have allowed a complete description of the strains during martensitic transformation, and the obtained conclusions can be extrapolated to other SMA systems. (c) 2019 Author(s).This work was supported by the Spanish Ministry of Economy and Competitiveness (No. MINECO MAT2017-84069-P), as well as by the Consolidated Research Group (No. IT-1090-16) and the ELKARTEK-ACTIMAT project from the Education and Industry Departments of the Basque Government. The University of the Basque Country (UPV/EHU) also supported this work with the Research Group GIU17/071. This work has benefited from the use of NPDF at the Lujan Center at Los Alamos Neutron Science Center, funded by the Department of Energy (DOE) Office of Basic Energy Sciences. Los Alamos National Laboratory is operated by Los Alamos National Security LLC, under DOE Contract No. DE-AC52-06NA25396. The upgrade of NPDF was funded by the National Science Foundation (NSF) through Grant No. DMR 00-76488

Superelastic damping at nanoscale in ternary and quaternary Cu-based shape memory alloys

Superelasticity is a characteristic thermomechanical property in shape memory alloys (SMA), which is due to a reversible stress-induced martensitic transformation. Nano-compression experiments made possible the study of this property in Cu-Al-Ni SMA micropillars, showing an outstanding ultra-high mechanical damping capacity reproducible for thousands of cycles and reliable over the years. This scenario motivated the present work, where a comparative study of the damping capacity on four copper-based SMA: Cu-Al-Ni, Cu-Al-Be, Cu-Al-Ni-Be and Cu-Al-Ni-Ga is approached. For this purpose, [001] oriented single crystal micropillars of comparable dimensions (around 1 mu m in diameter) were milled by focused ion beam technique. All micropillars were cycled up to two hundred superelastic cycles, exhibiting a remarkable reproducibility. The damping capacity was evaluated through the dimensionless loss factor eta, calculated for each superelastic cycle, representing the dissipated energy per cycle and unit of volume. The calculated loss factor was averaged between three micro-pillars of each alloy, obtaining the following results: Cu-Al-Ni eta = 0.20 +/- 0.01; Cu-Al-Be eta = 0.100 +/- 0.006; Cu-Al-Ni-Be eta = 0.072 +/- 0.004 and Cu-Al-Ni-Ga eta = 0.042 +/- 0.002. These four alloys exhibit an intrinsic superelastic damping capacity and offer a wide loss factor band, which constitutes a reference for engineering, since this kind of micro/nano structures can potentially be integrated not only as sensors and actuators but also as dampers in the design of MEMS to improve their reliability. In addition, the study of the dependence of the superelastic loss factor on the diameter of the pillar was approached in the Cu-Al-Ni-Ga alloy, and here we demonstrate that there is a size effect on damping at the nanoscale.This research was supported by the Spanish Ministry of Economy and Competitiveness, MINECO, projects MAT2017-84069P and CONSOLIDER-INGENIO 2010 CSD2009-00013, as well as by the ELKARTEK-CEMAP project from the Industry Department of the Basque Government, and GIU-17/071 from the University of the Basque Country UPV/EHU, Spain. This work made use of the FIB and ICP facilities of the SGIKER from the UPV/EHU. The author V.F. acknowledges the Post-Doctoral Mobility Grant from the CONICET of Argentina, and J.F.G.-C. also acknowledges the Post-Doctoral Grant (ESPDOC18/37) from the UPV/EHU

Internal friction associated with ε martensite in shape memory steels produced by casting route and through additive manufacturing: Influence of thermal cycling on the martensitic transformation

Among the different families of shape memory alloys (SMA), the Fe-Mn-Si-Cr-Ni alloys have attracted a renewed interest because of its low cost, high corrosion resistance and high recovery strength during the shape memory effect, and the new technologies of additive manufacturing offer unforeseen possibilities for this family of SMA. In the present work, the reversible gamma - epsilon martensitic transformation (MT), responsible for the shape memory effect, is studied in two Fe-Mn-Si-Cr-Ni alloys with high (20.2 wt%) and low (15.8 wt%) Mn content, produced by the conventional route of casting and rolling, in comparison with the MT in another similar alloy, with intermediate Mn content (19.4 wt%), which was produced by gas atomization and additive manufacturing through laser metal deposition. The forward and reverse gamma - epsilon MT is studied by mechanical spectroscopy through the internal friction spectra and the dynamic modulus variation, together with a parallel microstructural characterization including in-situ observation of the gamma - epsilon MT during cooling and heating at the scanning electron microscope. The evolution of the transformed fraction of epsilon martensite, evaluated through the integral area of the internal friction peak, was followed along thermal cycling in all three alloys. Both, the internal friction and the electron microscopy studies show that the epsilon martensite amount increases very fast during the first few cycles, and then decreases with a tendency towards its stabilization for many tens of cycles. The results show that the gamma - epsilon MT is more stable on cycling in the additive manufactured sample than in the conventionally processed samples, opening new avenues for designing shape memory steels to be specifically processed through additive manufacturing.This work was supported by the ELKARTEK-CEMAP (KK-2020/00047) project from the Industry Department of the Basque Government, and the GIU-17/071 from the University of the Basque Country, UPV/EHU. This work made use of the SGIKER facilities at the UPV/EHU

Designing for shape memory in additive manufacturing of Cu-Al-Ni shape memory alloy processed by laser powder bed fusion

Shape memory alloys (SMAs) are functional materials that are being applied in practically all industries, from aerospace to biomedical sectors, and at present the scientific and technologic communities are looking to gain the advantages offered by the new processing technologies of additive manufacturing (AM). However, the use of AM to produce functional materials, like SMAs, constitutes a real challenge due to the particularly well controlled microstructure required to exhibit the functional property of shape memory. In the present work, the design of the complete AM processing route, from powder atomization to laser powder bed fusion for AM and hot isostatic pressing (HIP), is approached for Cu-Al-Ni SMAs. The microstructure of the different processing states is characterized in relationship with the processing parameters. The thermal martensitic transformation, responsible for the functional properties, is analyzed in a comparative way for each one of the different processed samples. The present results demonstrate that a final post-processing thermal treatment to control the microstructure is crucial to obtain the expected functional properties. Finally, it is demonstrated that using the designed processing route of laser powder bed fusion followed by a post-processing HIP and a final specific thermal treatment, a satisfactory shape memory behavior can be obtained in Cu-Al-Ni SMAs, paving the road for further applications

Sociodemographic and Lifestyle Determinants of Adherence to Current Dietary Recommendations and Diet Quality in Middle-Aged Spanish Premenopausal Women

Background: A healthy diet when approaching menopause could prevent some of the symptoms associated with the climacteric. Few studies examine adherence to current healthy dietary recommendations in middle-aged premenopausal women. Our objective was to analyze the diet quality and the adherence to the Spanish Society of Community Nutrition (SENC) dietary recommendations in middle-aged Spanish premenopausal women, and to identify the associated sociodemographic and lifestyle factors. Methods: This is a cross-sectional study based on 1251 premenopausal women, aged 39-50, who attended to Madrid City Council Medical Diagnostic Center. Women completed an epidemiological and a food frequency questionnaire. Degree of adherence to the SENC recommendations was estimated with a score that evaluated null (0 points) and full (1 point) adherence of each specific recommendation. Associations were explored using an ordinal logistic multivariable regression model. Results: Regarding food groups, the worst adherence was found for sweets, red/processed meat, olive oil and eggs. Most of the participants exceeded the recommended caloric intake from proteins and fats, and practically all of them showed vitamin D intake deficiency. The overall score ranged from 2 to 12 (out of 15), with a median of 6.0 (interquartile range: 5.0-7.0). Former smokers (OR: 1.38; 95%CI: 1.08-1.78), as well as those with higher educational level (ORSSecondary:1.68; 95%CI: 0.97-2.93, ORUniversity:1.82; 95%IC: 1.05-3.14), with two or more children (OR: 1.31; 95%IC: 1.00-1.72), with higher caloric intake (OR>2188.2kcal/day: 8.22; 95%CI: 6.19-10.92) and with greater physical activity (OR≥21METS-h/week: 1.29; 95%CI: 0.95-1.76) showed greater adherence. Conclusions: Almost two-thirds of middle-aged premenopausal participants showed low or moderate compliance with SENC recommendations. Education, smoking, parity, and physical activity were associated with the degree of adherence to these recommendations.This study was funded by the Spanish Ministry of Health (EC11–273) and by the Instituto de Salud Carlos III (PI15CIII/0029). The article presents independent research.S

Veterinaria es Calidad

En una Universidad tan grande y antigua como la UCM donde las dinámicas de funcionamiento llevan décadas implantadas, la Cultura de la Calidad no ha sido entendida y acogida por una parte del colectivo universitario, que ve en ella una imposición, moda o, cuanto menos, la ruptura de una dinámica existente. Romper esta inercia depende de que todo el colectivo reconozca la necesidad y utilidad de estos métodos que permiten seguir avanzando adaptándose a una sociedad en continua evolución. Nuestro objetivo era que la comunidad universitaria del centro fuera consciente de la existencia de un sistema de calidad que era, en gran parte, responsable de las mejoras de las que todos disfrutamos