In-situ X-ray diffraction studies during growth of Ni-Ti shape memory alloy films and their complementary ex-situ characterization

Shape Memory Alloy (SMA) Ni-Ti films have attracted much interest as functional and smart materials due to their unique properties. However, there are still important issues unresolved like formation of film texture and its control as well as substrate effects. Thus, the main challenge is not only the control of the microstructure, including stoichiometry and precipitates, but also the identification and control of the preferential orientation since it is a crucial factor in determining the shape memory behaviour. The aim of this PhD thesis is to study the optimisation of the deposition conditions of films of Ni-Ti in order to obtain the material fully crystallized at the end of the deposition, and to establish a clear relationship between the substrates and texture development. In order to achieve this objective, a two-magnetron sputter deposition chamber has been used allowing to heat and to apply a bias voltage to the substrate. It can be mounted into the six-circle diffractometer of the Rossendorf Beamline (ROBL) at the European Synchrotron Radiation Facility (ESRF), Grenoble, France, enabling an in-situ characterization by X-ray diffraction(XRD) of the films during their growth and annealing. The in-situ studies enable us to identify the different steps of the structural evolution during deposition with a set of parameters as well as to evaluate the effect of changing parameters on the structural characteristics of the deposited film. Besides the in-situ studies, other complementary ex-situ characterization techniques such as XRD at a laboratory source, Rutherford backscattering spectroscopy(RBS), Auger electron spectroscopy (AES), cross-sectional transmission electron microscopy (X-TEM), scanning electron microscopy (SEM), and electrical resistivity (ER) measurements during temperature cycling have been used for a fine structural characterization. In this study, mainly naturally and thermally oxidized Si(100) substrates, TiN buffer layers with different thicknesses (i.e. the TiN topmost layer crystallographic orientation is thickness dependent) and MgO(100) single crystals were used as substrates. The chosen experimental procedure led to a controlled composition and preferential orientation of the films. The type of substrate plays an important role for the texture of the sputtered Ni-Ti films and according to the ER results, the distinct crystallographic orientations of the Ni-Ti films influence their phase transformation characteristics.

Laser welding of shape memory alloys

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Engenharia Mecânica

Vibration control with shape-memory alloys in civil engineering structures

Dissertação apresentada à Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Doutor em Engenharia Civil

A passagem à reforma : um estudo exploratório sobre mulheres profissionalizadas na sociedade portuguesa

RESUMO: Devido às mudanças políticas e sociais que ocorreram no passado, a proporção de mulheres activas no mercado de trabalho tem vindo a aumentar, e neste sentido, cada vez mais mulheres têm vindo a entrar na reforma. As recentes evoluções demográficas mostram um crescente envelhecimento populacional caracterizado por um aumento da proporção de pessoas idosas e pela sua maior longevidade. As mulheres são em número superior, no entanto, a realidade da mulher portuguesa reformada tem sido pouco avaliada sob o ponto de vista em que decorre esta transição. A passagem à reforma é um momento fulcral para conhecer como se adaptam os indivíduos a uma nova etapa da sua vida que é actualmente vivida por mais tempo, e que representa também a passagem para outra categoria social, a categoria de reformado. Condicionantes sociais, culturais e individuais, contribuem para modelar esta transição e o ajustamento à mesma. A reforma para as mulheres deverá corresponder a uma etapa com características únicas, devido às particularidades em termos profissionais e sociais que as distinguem dos homens. Pretende-se neste trabalho “dar voz” às mulheres portuguesas que tiveram uma carreira profissional e conhecer as suas experiências de transição para a reforma e a forma como vivem esta condição. Foram realizadas entrevistas em profundidade com mulheres portuguesas profissionais reformadas, cujos conteúdos foram analisados em torno das seguintes categorias: sentimentos vividos; planeamento e motivações para a passagem à reforma; relação com o trabalho; noção de si própria; gestão de tempo e organização quotidiana e interacções familiares e sociais.-------- ABSTRACT: Due to past political and social changes the number of women working actively in the labor market is growing. This implies that, more women are also entering in the retirement period. Recent demographic trends show an increasing ageing population, characterized by a higher proportion of elderly people, and a higher longevity. Women’s proportion outnumbers older men, yet the reality of Portuguese retired women has been poorly evaluated in regard to this transition process. Retirement transition is a crucial period to understand how individuals adapt to a new stage in their life, that is actually being enjoyed for a longer period and that also represents the transition to retiree’s social role. Social, cultural and individual conditions help to shape this transition and adjustment to it. Retirement for women should be an event with unique features, mostly because of the peculiarities in professional and social relationships, distinct from men. Through in-depth interviews, we explored how Portuguese women, who had a professional career, experience the retirement transition and how they live this new condition. The women’s narratives were analyzed within the following categories: experienced feelings, planning and motivation for retirement; notion of self; time management and daily organization; family and social interactions.

Correlation between the mechanical cycling behavior and microstructure in laser welded joints using NiTi memory shape alloys

Dissertação para obtenção do Grau de Mestre em Engenharia de Materiais

Neolithic transitions: can genetic data help us understand a major demographic event in human prehistory?

Dissertation presented to obtain the Ph.D degree in Biology

Glasses' makeup: the simple and the combined effect of color and shape on perceived volume and beverage intake

A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

Gas tungsten arc welding of NiTi shape memory alloy

Shape memory alloys are characterized by the ability of recovering their initial shape after being deformed and by superelasticity. Since the discovery of these alloys, a new field of interest emerged not only for the scientific community but also to many industries. However, these alloys present poor machinability which constitute a constrain in the design of complex components for new applications. Thus, the demand for joining techniques able to join these alloys without compromising their properties became of great importance to enlarge the complexity of existing applications. Literature shows that these alloys are joined mainly using laser welding. In the present study, similar NiTi butt joints, were produced using TIG welding. The welds were performed in 1.5 mm thick plates across the rolling direction. A special fixture and gas assist device was designed and manufactured. Also a robot arm was adapted to accommodate the welding torch to assure the repeatability of the welding parameters. Welds were successfully achieved without macroscopic defects, such as pores and distortions. Very superficial oxidation was seen on the top surface due to insufficient shielding gas flow on the weld face. The welded joints were mechanically tested and structurally characterized. Testing methods were used to evaluate macro and microstructure, as well as the phase transformation temperatures, the mechanical single and cyclic behaviour and the shape recovery ability. Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), microhardness measurements were techniques also used to evaluate the welded joints. A depletion in Ni in the fusion zone was seen, as well as a shift in Ms temperature. For strain values of 4% the accumulated irrecoverable strain was of about 30% and increased with the strain imposed during cycling. Nevertheless, a complete recovery of initial shape was observed when testing the shape memory effect on a dedicated device that introduces a deformation of 6.7%. That is, the welding procedure does not remove the ability of the specimens to recover their initial shape.

Information provision improvement with a geofencing event-bases system

Nowadays there is a big percentage of the population, specially young users, which are smartphone users and there is a lot of information to be provided within the applications, information provision should be done carefully and should be accurate, otherwise an overload of information will be produced, and the user will discard the app which is providing the information. Mobile devices are becoming smarter and provide many ways to filter information. However, there are alternatives to improve information provision from the side of the application. Some examples are, taking into account the local time, considering the battery level before doing an action and checking the user location to send personalized information attached to that location. SmartCampus and SmartCities are becoming a reality and they have more and more data integrated every day. With all this amount of data it is crucial to decide when and where is the user going to receive a notification with new information. Geofencing is a technique which allows applications to deliver information in a more useful way, in the right time and in the right place. It consists of geofences, physical regions delimited by boundaries, and devices that are eligible to receive the information assigned to the geofence. When devices cross one of these geofences an alert is pushed to the mobile device with the information.

The economic impact of the event Volta a Portugal em Bicicleta 2015

This thesis is a Field Lab project requested by the organizer of the Volta a Portugal em Bicicleta 2015, Podium Events. Its purpose is to determine the economic impact of the event for the 21 host economies and Portugal as a whole. The Volta started in Viseu and ended in Lisboa, and lasted for two weeks from the 29th July until the 8th August. Results were computed by accessing data provided by the different economic agents involved in the event (spectators, attendees and organizer), through face-to-face surveys and contact via e-mail. The Volta generated a total economic impact of €76.261.876. Keywords: Cycling,

Has the time for renewables finally arrived? – An event study on EPA’s Clean Power Plan

The recent proposals presented by EPA aimed to reduce the dependency of fossil fuels and to lower current emissions levels, hoping to gradually shift electric generation units to renewable energy sources. Actually, the Final Rule Proposal announcement day exhibited a negative Abnormal Return on Fossil Fuels but the following days had positive Abnormal Returns, mostly due to legislative change perceived by financial markets which eased up implementation periods of the proposed measures in the Final Rule when compared to the Draft Rule. Oppositely, Renewables and Solar Portfolios exhibited negative Cumulative Abnormal Returns over the period surrounding the Final Rule.

The economic impact of the event Volta a Portugal em Bicicleta 2015

This thesis is a Field Lab project requested by the organizer of the Volta a Portugal em Bicicleta 2015, Podium Events. Its purpose is to determine the economic impact of the event for the 21 host economies and Portugal as a whole. The Volta started in Viseu and ended in Lisboa, and lasted for two weeks from the 29th July until the 8th August. Results were computed by accessing data provided by the different economic agents involved in the event (spectators, attendees and organizer), through face-to-face surveys and contact via e-mail. The Volta generated a total economic impact of €76.261.876.