Rozprawy doktorskie na temat „ME MATERIALS”

This thesis, comprising of a written exegesis, solo exhibition and an artist book, emerged from research undertaken by an artist-researcher-teacher. For that reason, a/r/tography was the overarching methodology used, incorporating a bricolage of methods to address a multifaceted study undertaken in two settings: a primary school classroom and an artist’s studio. A/r/tography is a multilayered interdisciplinary Arts education research methodology that correlates well with my expertise as a primary Visual Arts specialist. The methodology allowed me to immerse myself in both teaching and the artmaking process, as ways of gaining a deeper understanding of Visual Arts pedagogy. The purpose of the study was to examine what the impact of making art with discarded materials had on raising environmental consciousness, from the viewpoint of an artist-researcher-teacher. Additionally, this research was positioned within the United Nations Decade of Education for Sustainable Development (2005–2014) and Sustainability, a cross-curriculum priority in the Australian Curriculum. The aim of this research was to show that Visual Arts is an effective way to embed Sustainability in the curriculum. In a two-phase study, the role of artmaking to facilitate shifts towards sustainability was investigated among 12-year-olds and myself in my creative praxis. In Phase One, 20 primary school students, from an area of high socio-economic advantage, participated in a 10-session Visual Arts program, using discarded materials to make and exhibit artworks with an environmental focus. Then, as an artist, I followed the same brief as the students, resulting in an exegesis and two creative components: an artist book incorporated into the exegetical writing and a solo exhibition at Edith Cowan University’s Spectrum Project Space in October 2014. This study showed that the creative reuse of discarded materials promoted reflexivity and raised sustainable awareness, leading to positive attitudinal and behavioural shifts in both the students and myself. The outcome of my creative component was a catalyst for shifts in the way I made art and the way I taught Visual Arts. By immersing myself in the artmaking process, I questioned unsustainable artmaking processes and moved towards reducing my own environmental footprint. The symbiotic nature of a/r/tography meant that new knowledge gained in the studio could be transferred to the classroom. The results of the research are presented through this exegetical writing and an exhibition, which included: returning to techniques that promoted reflexivity; exploring the ephemeral through photography; and demystifying the artmaking process through an artist book. The most significant finding of this study was that the physical act of artmaking enabled the students and me to re-examine our behaviours and to reconsider the value of discarded materials, which in turn triggered shifts in our awareness towards sustainability. Self-initiated behavioural shifts in the students included reusing materials and reducing consumption. Further, the students were able to make personal connections between their behaviours and their environmental footprints. This has implications for teachers integrating Sustainability. Arts-led education provides an alternative approach to teaching Sustainability across the curriculum. A set of recommendations arising from the research include: to provide support mechanisms to assist in-service teachers to implement Visual Arts-led Sustainability programs in primary schools; to introduce a/r/tography into pre-service teacher training; and for REmida WA to provide professional learning to support innovative, low-cost, multimodal in-service teacher training for Visual Arts-led Sustainability programs.

The oxide ion conductor bismuth vanadate (Bi₄V₂O₁₁) can be doped with various metal cations, Me²⁺ to Me⁶⁺; Me partially substitutes for vanadium to produce a new family of solid electrolytes known as BiMeVOX (Bismuth Metal Vanadium Oxides. Bi₄V₂O₁₁ is polymorphic having three forms α, β and γ; the high temperature form (γ) has high oxygen ion conductivity of comparable magnitude to existing solid electrolytes such as YSZ; however, this occurs at high temperatures (> 560°C). Doping Bi₄V₂O₁₁ with Me ions, leads to stabilisation of the γ-phase to room temperature, thus producing a material with promising practical applications. The parent material, Bi₄V₂O₁₁, is a non-stoichiometric phase forming a limited solid solution given by Bi_4+yV_2-yO_11-y; by virtue of the variable Bi:B ratio this leads to a range of compositions for the BiMeVOX materials and hence the overall formula Bi_4-yV_2-x-yMe_xO_11-y-σ. Thus, there is scope for a range of γ-phase compositions. The aims of this study were to - (1) investigate the Bi_4+yV_2-yO_11-y solid solution and formation of stoichiometric Bi₄V₂O₁₁ (i.e. y = 0); (2) optimise synthesis conditions of Me-doped Bi₄V₂O₁₁ (Me = W⁶⁺, Ta⁵⁺, Nb⁵⁺, Zr⁴⁺ and Ti⁴⁺); (3) determine the compositional extent of each solid solution formed by using a variety of diffraction, thermal and microscopic techniques; (4) investigate stabilisation, to room temperature, of the high temperature gamma (γ) phase, formed on doping Bi₄V₂O₁₁; (5) elucidate possible substitution mechanisms and initiate a crystallographic study of gamma phase materials. Bi₄V₂O₁₁ : It is shown that stoichiometric Bi₄B₂O₁₁ does not form, via solid state reaction, without precipitation of BiVoO₄ (scheelite) as secondary phase; a slight excess of Bi (y ≈ 0.02) is required to form single phase material in this system.

Ultrasound acoustic energy transfer (UAET) is an emerging contactless technology that offers the capability to safely and efficiently power sensors and devices while eliminating the need to replace batteries, which is of interest in many applications. It has been proposed to recharge and communicate with implanted medical devices, thereby eliminating the need for invasive and expensive surgery and also to charge sensors inside enclosed metal containers typically found in automobiles, nuclear power plants, space stations, and aircraft engines. In UAET, energy is transferred through the reception of acoustic waves by a piezoelectric receiver that converts the energy of acoustic waves to electrical voltage. It has been shown that UAET outperforms the conventional CET technologies that use electromagnetic waves to transfer energy, including inductive coupling and capacitative coupling. To date, the majority of research on UAET systems has been limited to modeling and proof-of-concept experiments, mostly in the linear regime, i.e., under small levels of acoustic pressure that result in small amplitude longitudinal vibrations and linearized piezoelectricity. Moreover, existing models are based on the "piston-like" deformation assumption of the transmitter and receiver, which is only accurate for thin disks and does not accurately account for radiation effects. The linear models neglect nonlinear effects associated with the nonlinear acoustic wave propagation as well as the receiver's electroelastic nonlinearities on the energy transfer characteristics, which become significant at high source strengths. In this dissertation, we present experimentally-validated analytical and numerical multiphysics modeling approaches aimed at filling a knowledge gap in terms of considering resonant acoustic-piezoelectric structure interactions and nonlinear effects associated with high excitation levels in UAET systems. In particular, we develop a reduced-order model that can accurately account for the radiation effects and validate it by performing experiments on four piezoelectric disks with different aspect ratios. Next, we study the role of individual sources of nonlinearity on the output power characteristics. First, we consider the effects of electroelastic nonlinearities. We show that these nonlinearities can shift the optimum load resistance when the acoustic medium is fluid. Next, we consider the nonlinear wave propagation and note that the shock formation is associated with the dissipation of energy, and as such, shock formation distance is an essential design parameter for high-intensity UAET systems. We then present an analytical approach capable of predicting the shock formation distance and validate it by comparing its prediction with finite element simulations and experimental results published in the literature. Finally, we experimentally investigate the effects of both the nonlinearity sources on the output power characteristics of the UAET system by considering a high intensity focused ultrasound source and a piezoelectric disk receiver. We determine that the system's efficiency decreases, and the maximum voltage output position drifts towards the source as the source strength is increased.
Doctor of Philosophy
Advancements in electronics that underpinned the development of low power sensors and devices have transformed many fields. For instance, it has led to the innovation of implanted medical devices (IMDs) such as pacemakers and neurostimulators that perform life-saving functions. They also find applications in condition monitoring and wireless sensing in nuclear power plants, space stations, automobiles and aircraft engines, where the sensors are enclosed within sealed metal containers, vacuum/pressure vessels or located in a position isolated from the operator by metal walls. In all these applications, it is desired to communicate with and recharge the sensors wirelessly. Such a mechanism can eliminate the need for invasive and expensive surgeries to replace batteries of IMDs and preserve the structural integrity of metal containers by eliminating the need for feed through wires. It has been shown that ultrasound acoustic energy transfer (UAET) outperforms conventional wireless power transfer techniques. However, existing models are based on several assumptions that limit their potential and do not account for effects that become dominant when a higher output power is desired. In this dissertation, we present experimentally validated numerical and theoretical investigations to fill those knowledge gaps. We also provide crucial design recommendations based on our findings for the efficient implementation of UAET technology.

Duplex stainless steels, DSS are stainless steels that consist of the two phases austenite and ferrite.  The DSS have superb properties and are widely used in industries such as nuclear power and in pressure vessels, pipes and in pipelines.  The use of DSS are limited due to embrittlement which occurs at temperatures from 250 to 550 oC. This imposes a general limited service temperature of 250 oC. The mechanism mainly responsible for the embrittlement is a phase separation occurring in the ferrite phase. Furthermore, there is a direct link between the phase separation and the mechanical properties:  the ferrite hardness increases whereas the toughness decreases under low temperature aging.  In this thesis, the low-temperature embrittlement of duplex stainless  steels  was  studied  through  machine learning  modelling  and  experimental hardness-  and  microscopy measurements.   The  resulting  model  describes  the  data with an accuracy, R-squared = 0.94.  In combination with the experimental results, nickel  was identified  as  an  important  parameter  for  the  hardness  evolution.   This work aims to provide a fundamental study for understanding the importance of alloying elements on the phase separation in DSS, and provides a new methodology via a combination of machine learning and key experiments for the material design.
Duplexa rostfria stål är rostfria stål som består av de båda faserna ferrit och austenit. De har extraordinära egenskaper och används brett inom industrin, t ex. i kärnkraftverk och  i  tryckkärl  och  pipelines.  Användningen av  duplexa  rostfria stål  är  begränsad p.g.a.  försprödning som uppstår i legeringarna vid temperaturer mellan 250-550 oC, vilket  medför  att  den  tillåtna  temperaturen  vid  användning  begränsas  till  under 250 oC.  Den  främsta  orsaken  till  försprödningen  är  en  fasseparation  i  den  ferrita fasen under åldring vid låg temperatur.  Vidare leder fasseparationen till mekaniska förändringar i ferritfasen: hårdheten  ökar  medan  segheten  minskar.   I  den här  rapporten  undersöks försprödningen  av  duplexa  rostfria  stål  vid  åldring  med hjälp av datormodellering med maskininlärning samt av experimentella hårdhets- och mikroskopiska  mätningar.   Modellen  hade  en  noggrannhet  (determinationsko- efficienten,  R2)  på  0.94.   Resultatet  från  modellen  visade  tillsammans  med de  experimentella  resultaten  att  nickel  är  ett  legeringsämne  som  har  stor betydelse  för hårdhetsökningen.  Detta  arbete  syftar  till  att  utgöra  en grundläggande  studie  för att förstå påverkan från olika legeringsämnen på fasseparationer i DSS, och bidrar med en ny metodik för materialdesign som kombinerar maskininlärning och utvaldaexperiment.
EIT RawMaterial Project ENDUREIT

The forest is teeming with activity: fungi transform dead logs into nutrients, roots entangle themselves with the earth, and strong winds break resilient boughs. Like the forest, the human body functions according to a complex system of agents - from the micro bacteria in the gut to the pores of the skin. The built world has often been rendered in opposition to these processes of nature. As a vessel through which the world is experienced, the body is an intermediary between raw matter and fabricated things. The planet is suffused with human life, and there is a critical tension between human production and the well-being of the biosphere. Is there an ecological benefit to dissolving the division between the human-made and the organic? My exhibition, I Thought the Earth Remembered Me, integrates the ambiguous forms of the forest into mass-produced sheetrock walls in order to break down the boundary between the built and natural world. Through making, I hope the work unearths a way to be enchanted on a damaged planet.

Wearable technologies are being adopted in increasing numbers and the market space appears poised for continued growth in virtually all areas, from medicine, to self-quantification, to sports. While the overwhelming majority of work on wearables has been done on their medical applications and their role in shaping identity, this dissertation examines the roles that wearable technologies play on the decision-making processes in athletic contexts. Using new materialism and Actor Network Theory as lenses, I attempt to break from the Cartesian model that places human subjectivity and intentionality at the center of a rhetorical situation and, rather, allow that non-human actants are agentive. I examine the interactions that age-group triathletes have with their wearable technologies and the shifting agencies that accompany those interactions. These interactions call on disparate human and non-human actors in forming a series of temporary, shifting networks that utilize a distributed agency in the decision making process.

Myalgic encephalomyelitis (ME), also referred to as chronic fatigue syndrome (CFS), is a symptomatically defined and debilitating condition that presents as a range of physiological and psychological effects. Post-exertional fatigue and ongoing low energy levels are cardinal features. Whilst ME-like conditions have been recognised for at least two hundred years, they have been characterised over recent decades by a fiercely contested debate as to whether aetiology is primarily psychological or physiological. ME sufferers experience profound changes to their self-perception, ability to maintain daily routines and activities and how they are perceived in terms of their capacity to carry out social roles, including illness-status. The contested aetiology results in-part from a climate of dualistic thought and the biomedical model upon which ME is treated and theorised. Whilst the effects of ME on self experience have been investigated from various qualitative and quantitative perspectives, the primary purpose of this thesis is to develop a psychosocial framework from which to explore previously neglected dimensions of the effect of ME on self experience. Developing a psychosocial understanding of ME is in keeping with a turn towards post-Cartesian and non-dualistic thinking. The second interconnected purpose of this thesis is to address the role played by the material environment and objects and to conceptualise their importance and relation to self and how it is affected by ME. This is currently absent in the literature on ME. Developing a psychosocial framework suitable for this purpose rested on a synthesis of Actor Network Theory (ANT) and a psychoanalytically influenced use of metaphor and metonymy. At the heart of this synthesis are the notions of relational ontology (Latour, 1997; DeLanda, 2002) and assemblage (Deleuze and Guattari, 1987; DeLanda, 2002; Hodder, 2012). A relational ontology focuses on the relations between disparate objects such as material artefacts, humans, other organisms and concepts and avoids prioritising any one ‘thing’ as more important than another. The notion of assemblage has emerged alongside ideas concerning complexity, chaos and indeterminacy and informs a vocabulary addressing the problem of causality, determination and the stability of social and psychological phenomena (Venn, 2006). As part of a psychoanalytically informed psychosocial framework these concepts enable an exploration of ME by bringing together disparate aspects such as everyday objects, experiences, symptoms and environments in a non-causal, non-dualistic and processual manner. The psychoanalytic element also enables an exploration of the unconscious and irrational aspects of experience, which is most pertinent with regards to the effects of ME. Thus, the premise of this research was to establish a psychosocial methodology and theoretical basis from which to explore the effects of ME on self experience. Moreover, this methodology was designed to engage with the complex, coincident and entangled nature of the symptoms, discourses, objects, material artefacts, environments and non-human organisms that ME appears to be comprised of. Methods were developed which enabled the researcher to be with and explore the day-to-day life and routines of eight ME sufferers in their everyday environments over a six month period. This involved working with the ME sufferers taking part primarily in their own homes and spaces around their home which they frequented, such as shopping malls and even a cemetery; in itself novel in terms of qualitative research into ME. Of these eight sufferers, three were male [age range 49 – 65; earliest formal diagnosis of ME occurring in 2005] and five females [age range 25 – 63; earliest diagnosis 2002]. Two sufferers were in paid employment, one was retired and five were unable to work due to their ME. Due to the extensive nature of the data, only 3 case studies, two male and three female, were selected for in-depth analysis. Cases selected were those that most clearly illustrated central analytic themes. Data comprised talk, audio-visual material and the affective responses of the researcher. Analytic methods were devised which initially adopted a thematic approach before metaphoric and metonymic equivalences were drawn between what ME sufferers discussed and aspects of the routines, objects and environments they were engaged with. This informed descriptions of how these things became networked, in an ANT sense, and how self experience was implicated. A key finding which emerged is the notion of debilitating spaces. This term captures the manner in which, for certain sufferers, the experience and hence the maintenance of ME was intrinsically enmeshed with their immediate physical environment. Further findings discussed include the way in which seemingly everyday objects such as food blenders can be co-opted by sufferers as a means of enhancing their self-experience in light of ME. Overall, the findings of this PhD are discussed in terms of the success and applicability of that premise and its contribution to the field of psychosocial approaches. The key assertion is that the methodology enhances an understanding of ME and its effects, highlighting the variable yet particular nature of ME and its effect on self experience and in incorporating the hitherto unconsidered range of objects outlined above.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Este trabalho é resultado de minha experiência como integrante de equipe de Design de Produção da TV Globo e de minha participação no grupo de estudo sobre Design & Envelhecimento do Laboratório de Pesquisa Aplicada de Design, Memória e Emoção da PUC-Rio. Ele está fundamentado em premissas da Antropologia do Consumo e na ideia de que nosso universo material é a expressão de nossa cultura, crenças, valores, estilos de vida e personalidades e traz o registro de visitas a casas de idosos fictícios e idosos reais. As visitas a idosos da ficção foram realizadas nas casas das personagens Nenê (interpretada pela atriz Marieta Severo), Darlene (interpretada pela atriz Marília Pera), Violeta (interpretada pela atriz Glória Menezes) e Picucha (interpretada pela atriz Fernanda Montenegro). Essas visitas tiveram como base os procedimentos da atividade do Design de Produção que, junto com Cenografia e Figurino, monta a casa e as coisas das personagens a partir de seus respectivos perfis e sinopses. As visitas a idosos reais, por sua vez, foram realizadas na casa de nove moradores na Gávea, bairro da zona sul do Rio de Janeiro, e incluíram técnicas de observação participante e entrevistas etnográficas. Elas tiveram como base o caminho inverso percorrido pela atividade do Design de Produção e buscaram montar os perfis dos idosos reais a partir de suas casas e coisas. Este trabalho foi motivado pelo crescente e irreversível fenômeno do envelhecimento e longevidade populacional e pela constatação de que, apesar de numeroso e diverso o público com mais de 60 anos ainda é tratado como homogêneo. A imagem do velho frágil, doente e dependente e associada a asilos, bengalas, cadeiras de roda e fraldas geriátricas está em processo de mudança, mas ainda é recorrente em conversas, telas e páginas. Neste sentido, este trabalho pretende propor um método para conhecer as pessoas para quem se projeta em geral, e os idosos em particular, a partir de suas casas e coisas. Ele tem como missão contribuir com a construção de uma visão mais positiva, ampla e plural sobre a velhice e seu universo material.
This work is the result of my experience as a member of TV Globo s Production Design team of and my participation in the study group focused on Design & Aging in the Applied Research Laboratory of Design - Memory and Emotion of PUC-Rio. It brings reflections based on assumptions of the Anthropology of Consumption and on the idea that our material universe is the expression of our identity and our culture, beliefs, values, lifestyles and personalities. It also documents visits to homes of fictional elders and real elders. The fiction elders visits were held in the homes of the following characters: Nenê (played by Marieta Severo), Darlene (played by Marilia Pera), Violeta (played by Gloria Menezes) and Picucha (played by Fernanda Montenegro). They were based on Production Design procedures , that together with Set Design and Costume Design, build the house and characters things based on their respective profiles and synopses. The visits to the real elders homeswere conducted in nine residences in Gávea, neighborhood of Rio de Janeiro, and included participant observation techniques and ethnographic interviews. They were based on the reverse path taken by the activity of the Production Design and sought assemble profiles of real elders from their homes and things. This work was motivated by the growing and irreversible phenomenon of populational aging and longevity and by the fact that, despite numerous and diverse the audience over 60 years old is still treated as homogeneous. The image of the frail elder, sick and dependent is associated with nursing homes, canes, wheelchairs and adult diapers is in process of change, but it is still recurring in conversations, screens and pages. This work aims to propose a method to know the people for whom projects in general and the elderly in particular, from their homes and things. It s mission is to contribute to build a positive view, broad and plural about elderly and its material universe.

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Este trabalho discute os percursos adotados pelos professores autores/conteudistas ao produzirem seus respectivos materiais didáticos do Programa E-Tec Brasil que oferta cursos técnicos na modalidade a distância, desde a concepção do desenho didático do curso, as diretrizes da Instituição a orientar seus professores para as produções, até os resultados desses materiais elaborados pelos professores sob as orientações dos coordenadores dos cursos. Partimos da hipótese que os professores ainda tenham construções de materiais didáticos para EaD perante uma concepção Fordista/Tradicional, o que aponta um não aproveitamento na base de uma construção construtivista. Como aporte teórico, apresentamos discussões sobre a Sociedade da Informação e em Rede, Castells (2009). Discutimos também sobre as transformações da educação atendendo a sociedade em transformação, sobretudo, a partir da modalidade de educação a distância. Em tempo, seu percurso histórico, as suas transformações a partir das novas tecnologias digitais, baseados em Moore e Kearsley (2011), Maia e Mattar (2007), e na perspectiva da Educação Online com Santos (2010) e Silva (2012). Discutimos também, o desenho didático Instrucional/Educacional de cursos com Filatro (2009) e Mattar (2012) e os papéis dos que estão envolvidos para uma prática de produção de materiais didáticos, promovendo interações e interatividade sobre o olhar de Primo (2008) e Silva (2012). Também discutimos propostas de materiais didáticos para EaD que favorecem o sociointeracionismo respaldados em Vilardi (2005), Palange (2009) e Fernandez (2009). Com base nesses marcos teóricos, a pesquisa propõe revelar desde as concepções no Programa ETec como política pública ao apontar os autores envolvidos para a efetivação dessas construções, assim como, analisar as orientações estabelecidas pela Instituição que oferta estes cursos para a efetivação dessas produções. Respondendo a esses questionamentos, adotamos a entrevista com os sujeitos que eram responsáveis diretamente na produção desses materiais, como coordenadora de curso e designer instrucional/educacional, assim como os professores autores/conteudistas diretamente envolvidos com as produções desses materiais. Foram analisados os percursos e as interações adotadas pelo professor autor/conteudista ao produzir seu material. A análise documental foi utilizada como instrumento de coleta para analisar a veracidade dos documentos oficiais Institucionais e os documentos produzidos pelos professores (materiais didáticos). O método de análise foi a análise de conteúdo, baseado em Moraes (1997) e Bardin (2011). Os resultados da pesquisa apontam o quanto o desenho didático do curso “engessa” o processo de produção dos materiais didáticos, visto que são lineares e instrucionistas, assim como, as interações dos alunos com as demais produções (vídeos aulas, atividades) estão orientados com interações apenas com conteúdos, conduzindo os educandos a fixação dos conteúdos como estratégia de aprendizagem.

Despite significant efforts have been directed toward reducing waste generation and encouraging alternative waste management strategies, landfills still remain the main option for Municipal Solid Waste (MSW) disposal in many countries. Hence, landfills and related impacts on the surroundings are still current issues throughout the world. Actually, the major concerns are related to the potential emissions of leachate and landfill gas into the environment, that pose a threat to public health, surface and groundwater pollution, soil contamination and global warming effects. To ensure environmental protection and enhance landfill sustainability, modern sanitary landfills are equipped with several engineered systems with different functions. For instance, the installation of containment systems, such as bottom liner and multi-layers capping systems, is aimed at reducing leachate seepage and water infiltration into the landfill body as well as gas migration, while eventually mitigating methane emissions through the placement of active oxidation layers (biocovers). Leachate collection and removal systems are designed to minimize water head forming on the bottom section of the landfill and consequent seepages through the liner system. Finally, gas extraction and utilization systems, allow to recover energy from landfill gas while reducing explosion and fire risks associated with methane accumulation, even though much depends on gas collection efficiency achieved in the field (range: 60-90% Spokas et al., 2006; Huitric and Kong, 2006). Hence, impacts on the surrounding environment caused by the polluting substances released from the deposited waste through liquid and gas emissions can be potentially mitigated by a proper design of technical barriers and collection/extraction systems at the landfill site. Nevertheless, the long-term performance of containment systems to limit the landfill emissions is highly uncertain and is strongly dependent on site-specific conditions such as climate, vegetative covers, containment systems, leachate quality and applied stress. Furthermore, the design and operation of leachate collection and treatment systems, of landfill gas extraction and utilization projects, as well as the assessment of appropriate methane reduction strategies (biocovers), require reliable emission forecasts for the assessment of system feasibility and to ensure environmental compliance. To this end, landfill simulation models can represent an useful supporting tool for a better design of leachate/gas collection and treatment systems and can provide valuable information for the evaluation of best options for containment systems depending on their performances under the site-specific conditions. The capability in predicting future emissions levels at a landfill site can also be improved by combining simulation models with field observations at full-scale landfills and/or with experimental studies resembling landfill conditions. Indeed, this kind of data may allow to identify the main parameters and processes governing leachate and gas generation and can provide useful information for model refinement. In view of such need, the present research study was initially addressed to develop a new landfill screening model that, based on simplified mathematical and empirical equations, provides quantitative estimation of leachate and gas production over time, taking into account for site-specific conditions, waste properties and main landfill characteristics and processes. In order to evaluate the applicability of the developed model and the accuracy of emissions forecast, several simulations on four full-scale landfills, currently in operative management stage, were carried out. The results of these case studies showed a good correspondence of leachate estimations with monthly trend observed in the field and revealed that the reliability of model predictions is strongly influenced by the quality of input data. In particular, the initial waste moisture content and the waste compression index, which are usually data not available from a standard characterisation, were identified as the key unknown parameters affecting leachate production. Furthermore, the applicability of the model to closed landfills was evaluated by simulating different alternative capping systems and by comparing the results with those returned by the Hydrological Evaluation of Landfill Performance (HELP), which is the most worldwide used model for comparative analysis of composite liner systems. Despite the simplified approach of the developed model, simulated values of infiltration and leakage rates through the analysed cover systems were in line with those of HELP. However, it should be highlighted that the developed model provides an assessment of leachate and biogas production only from a quantitative point of view. The leachate and biogas composition was indeed not included in the forecast model, as strongly linked to the type of waste that makes the prediction in a screening phase poorly representative of what could be expected in the field. Hence, for a qualitative analysis of leachate and gas emissions over time, a laboratory methodology including different type of lab-scale tests was applied to a particular waste material. Specifically, the research was focused on mechanically biologically treated (MBT) wastes which, after the introduction of the European Landfill Directive 1999/31/EC (European Commission, 1999) that imposes member states to dispose of in landfills only wastes that have been preliminary subjected to treatment, are becoming the main flow waste landfilled in new Italian facilities. However, due to the relatively recent introduction of the MBT plants within the waste management system, very few data on leachate and gas emissions from MBT waste in landfills are available and, hence, the current knowledge mainly results from laboratory studies. Nevertheless, the assessment of the leaching characteristics of MBT materials and the evaluation of how the environmental conditions may affect the heavy metals mobility are still poorly investigated in literature. To gain deeper insight on the fundamental mechanisms governing the constituents release from MBT wastes, several leaching experiments were performed on MBT samples collected from an Italian MBT plant and the experimental results were modelled to obtain information on the long-term leachate emissions. Namely, a combination of experimental leaching tests were performed on fully-characterized MBT waste samples and the effect of different parameters, mainly pH and liquid to solid ratio (L/S,) on the compounds release was investigated by combining pH static-batch test, pH dependent tests and dynamic up-flow column percolation experiments. The obtained results showed that, even though MBT wastes were characterized by relatively high heavy metals content, only a limited amount was actually soluble and thus bioavailable. Furthermore, the information provided by the different tests highlighted the existence of a strong linear correlation between the release pattern of dissolved organic carbon (DOC) and several metals (Co, Cr, Cu, Ni, V, Zn), suggesting that complexation to DOC is the leaching controlling mechanism of these elements. Thus, combining the results of batch and up-flow column percolation tests, partition coefficients between DOC and metals concentration were derived. These data, coupled with a simplified screening model for DOC release, allowed to get a very good prediction of metal release during the experiments and may provide useful indications for the evaluation of long-term emissions from this type of waste in a landfill disposal scenario. In order to complete the study on the MBT waste environmental behaviour, gas emissions from MBT waste were examined by performing different anaerobic tests. The main purpose of this study was to evaluate the potential gas generation capacity of wastes and to assess possible implications on gas generation resulting from the different environmental conditions expected in the field. To this end, anaerobic batch tests were performed at a wide range of water contents (26-43 %w/w up to 75 %w/w on wet weight) and temperatures (from 20-25 °C up to 55 °C) in order to simulate different landfill management options (dry tomb or bioreactor landfills). In nearly all test conditions, a quite long lag-phase was observed (several months) due to the inhibition effects resulting from high concentrations of volatile fatty acids (VFAs) and ammonia that highlighted a poor stability degree of the analysed material. Furthermore, experimental results showed that the initial waste water content is the key factor limiting the anaerobic biological process. Indeed, when the waste moisture was lower than 32 %w/w the methanogenic microbial activity was completely inhibited. Overall, the obtained results indicated that the operative conditions drastically affect the gas generation from MBT waste, in terms of both gas yield and generation rate. This suggests that particular caution should be paid when using the results of lab-scale tests for the evaluation of long-term behaviour expected in the field, where the boundary conditions change continuously and vary significantly depending on the climate, the landfill operative management strategies in place (e.g. leachate recirculation, waste disposal methods), the hydraulic characteristics of buried waste, the presence and type of temporary and final cover systems.

The upsurge in energy usage in the field of electronics and communication has increased dependency on storage of energy from renewable as well as nonrenewable sources. Consequently, the major need of the world is to prepare efficient materials capable of storing and providing environment friendly sustainable and clean energy. Different research groups have put strenuous efforts for the preparation of advanced electronic materials as cheaper and alternative for energy storage elements in which batteries have up surged but the main focus is on the fabrication of dielectric materials with remarkable charging and discharging capacities and thermal stability. In context of energy storage devices, ceramics are found to exhibit outstanding electrical properties, prominent stability, and high rigidity under severe environmental conditions. The electrical energy storage application requires that these materials exhibit strong and large spontaneous polarization (Ps) as well as low remnant polarization. The dielectrics and ferroelectrics exhibit strong energy storage property and are subsequently desired in modern electrics and pulsed capacitors for power electronic system. Dielectric materials display excellent power density and strong discharge capability. In this context, oxide-based systems have inspired to show good results in these applications. In recent years, various types of lead-free ceramic materials based on titanate are extensively investigated because of their important applications in energy storage devices. The probing of multifunctional materials with energy storage property is essential for technological advancements. Among these viii materials, there exist unique magnetoelectric (ME) materials, which display controlling attribute of manipulation of ferroelectric ordering by applied magnetic field or ferromagnetic ordering by applied electric field. The first artificial ME material was an eutectic composite of BaTiO3 and CoFe2O4, which was formed by mixing the ferroelectric and ferromagnetic constituents. The implemented magnetic field and the voltage generated do not vary linearly as in the case of single-phased compounds due to the complexity of ME coupling amongst these phases. The research on ME coupling of composite materials has been thoroughly investigated. An enormous effort has been focused on materials with large ME effect in the field of physics and material science for building new types of multistate memory devices. There are two classes of ME materials: Single phase magnetoelectrics and two-phase magnetoelectrics. Single phase ME materials show the coupling in a single phase material where the coupling arises out of two or more ferroic orders. Further, two phase magnetoelectrics or composite ME exhibit large magnitudes of the ME voltage and are therefore preferred over single phase magnetoelectrics. Usually, a ME composite consists of ferroelectric and ferromagnetic for piezoelectricity and magnetostriction to exhibit multiferroism. The composite ME materials exhibit tensorial product property as a consequence of mutually connected electric and magnetic phases resulting in indirect mechanical strain transfer at the interface of two phases and enhanced ME coupling. Motivated by the above-mentioned facts, different magnetic material based - BaTiO3 composites have been synthesized by solid state reaction ix route by varying the composition to explore the magnetoelectric properties comprehensively. Dielectric, ferroelectric and energy storage properties have also been discussed in detail. Based on the extensive characterization and measured physical properties, the outcome of the research work has been organized into eight chapters and the chapter wise summary of the same is as follows: Chapter 1 begins with a brief introduction, origin of problem, motivation for the research work and an overview of the current work. This chapter includes origin of magnetoelectricity and multiferroics. Subsequently, the types of magnetoelectric materials and importance of the composite materials have been discussed in detail. The following section describes about the structure of perovskite and spinel materials. The electrical and magnetic properties of materials have been discussed briefly. A short description on importance of BaTiO3 and ferrimagnetic (CoFe2O4 and Co0.5Ni0.5Fe2O4), ferromagnetic (Bi0.85La0.15FeO3) and antiferromagnetic (NdMnO3) materials have also been discussed in this chapter. Finally, the objectives of the thesis based on the review of the literature have been incorporated. Chapter 2 describes the synthesis procedure and characterization techniques used in the current thesis. The solid state reaction method has been used to synthesize desired perovskite BaTiO3, magnetic constituents (CoFe2O4, Co0.5Ni0.5Fe2O4, Bi0.85La0.15FeO3 and NdMnO3) and their composites. The stoichiometry in these composites has been varied to enhance the obtained magnetoelectric coupling and energy storage x properties. This chapter elaborates the utility of many sophisticated experimental techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, dielectric LCR meter and Impedance analyzer, vibrating sample magnetometer (VSM) and P-E ferroelectric hysteresis loop tracer in order to study the various properties such as structural, morphological, dielectric, magnetic, ferroelectric, magnetoelectric and energy storage properties, respectively. Chapter 3 presents the comprehensive study on the composites of BaTiO3-CoFe2O4 (BT-CFO) for energy storage and magnetoelectric applications. This chapter focuses on the basic ferroelectric BaTiO3 (BT) and the effect of ferrite composition on magnetoelectric and energy storage properties of BT. The structural and morphological optimization of BT-CFO was systematically studied to obtain bi-phasic ferroelectric-ferrite system. The dielectric studies revealed Maxwell-Wagner polarization and thermal activated non-Debye type relaxation process in BT-CFO composites with 0.95BT - 0.05CFO composite exhibiting low dielectric loss ≈ 0.3 in frequency range of 100 Hz - 1 MHz and promised for industrial application. The maximum value of magneto-dielectric coupling achieved was 1.2 % at 7 kOe for 0.95BT - 0.05CFO composite. The impedance and conduction studies revealed high resistive nature in the composites and dominant polaron tunneling conduction mechanism. The ferroelectric P–E loop measurement confirmed the ferroelectric nature in BT-CFO composites. The maximum energy storage density and efficiency achieved for 0.95BT - 0.05CFO composite were 8.33 mJ/cm3 and 59.7 % respectively. The xi magnetoelectric coupling coefficient (α) was estimated by studying the effect of magnetic field on ferroelectric hysteresis loop measurements. The value of α was the highest for 0.95BT - 0.05CFO composite and was 13.33 mV/cm/Oe. The enhanced dielectric, ferroelectric, magnetoelectric characteristics suggest the scope of BT-CFO composites in energy storage applications. (The results of this chapter have been published in Journal of Mater Sci: Mater Electron 29 (2018) 18352–18357 (IF: 2.22) and Materials Chemistry and Physics 234 (2019) 110–121 (IF: 3.408)). Chapter 4 describes the multiferroic and magnetoelectric properties of CoFe2O4-BaTiO3 (CFO-BT) for energy storage and magnetoelectric applications. This chapter focuses on basic ferromagnetic CFO and the effect of ferroelectric BT concentration on magnetoelectric and energy storage properties of CFO. The composites of CFO-BT exhibited interplay of magnetism, ferroelectricity and display strong magnetoelectric behavior arising out of charge disordering. The structural analysis from the combination of XRD, Raman, and FT-IR measurements of CFO-BT composites established the co-existence of cubic and tetragonal phases. The dielectric measurements confirmed non-Debye type Maxwell-Wagner polarization and temperature-dependent relaxation in CFO-BT composites with 0.7CFO - 0.3BT composite showing an unexpected low dielectric loss ≈ 0.5 above 1 kHz and exhibited potential for device applications. The magnetic measurements revealed an enormous increase in the coercivity of 0.7CFO - 0.3BT composite, which was identified in terms of movement of ferromagnetic domains arising due to inclusion of trapping centers of BT in CFO. The impedance spectroscopy and conductivity measurements xii confirmed high impedance behavior and crossover from barrier hopping to polaron conduction in CFO-BT composites. The addition of BT in CFO initiated the structural modification and resulted in conductivity cross-over with improved conductivity. The ferroelectric properties displayed a low leakage charge density of 0.0031 mC/cm2 and prevalent asymmetry arising due to spatial disordering of charge distribution. The maximum energy storage density and efficiency achieved for 0.7CFO - 0.3BT composite were 3.009 mJ/cm3 and 27.3 % respectively. The highest value of α obtained was 22 mV/cm/Oe at a field of 5000 Gauss for 0.9CFO - 0.1BT composite. These results were useful for exploring energy storage devices based on magnetoelectric CFO-BT composites. (The results of this chapter have been published in Journal of Alloys and Compounds 779 (2019) 918-925 (IF: 4.65) and Journal of Electronic Materials 49 (2020) 472–484 (IF: 1.774)). Chapter 5 deals with magnetoelectric bulk composites of Co0.5Ni0.5Fe2O4-BaTiO3 (CNFO-BT). The structural studies of CNFO-BT composites confirmed lattice distortion and enlarged strain owing to increasing BT in CNFO. The dielectric and impedance measurement exhibited conventional Maxwell-Wagner polarization and confirmed the existence of grain dominated non-Debye relaxations phenomena in CNFOBT composites. The magnetic hysteresis curves revealed strong ferromagnetic behavior in all composites. The maximum energy storage density and efficiency achieved for 0.8CNFO - 0.2BT composite were 4.25 mJ/cm3 and 31.6 % respectively. The highest value of magnetoelectric coupling obtained was 5 mV/cm/Oe at a field of 4000 Oersted for 0.8CNFO - 0.2BT composite. These results revealed lattice distortion, interfacial xiii charge polarization and restricted ferromagnetic domain wall rotation arising from substitution of BT in CNFO and indicate that CNFO-BT composites have potential for energy storage applications. (The results of this chapter have been communicated to Journal of Electroceramics (IF: 2.58)). Chapter 6 focused on the comprehensive study of Bi0.85La0.15FeO3- BaTiO3 (BLFO-BT) for magnetoelectric and energy storage applications. The structural analysis revealed phase purity in BLFO and a structural transformation from rhombohedral to cubic phase with increasing content of BT confirming the co-existence of composite phase with lattice compression. The dielectric measurements displayed peak broadening in temperature–permittivity plot and confirm relaxor behavior in BLFO-BT composite ceramics. The magnetic measurements confirmed the existence of weak ferromagnetism in BLFO-BT composites and novel superparamagnetism in 0.9BLFO - 0.1BT composite ceramic. The ferroelectric hysteresis P-E loop measurements produced unsaturated ovalshaped loops with high leakage and displayed a lossy dielectric nature. The 0.9BLFO - 0.1BT composite displayed an improved recoverable energy storage density of 16 mJ/cm3 with an improved efficiency of 60 %. The highest value of magnetoelectric coupling obtained was 16 mV/cm/Oe at a field of 3000 Oersted for 0.9BLFO - 0.1BT composite. The superparamagnetic behavior and magnetic field-dependent energy storage capacity of BLFO-BT composite ceramics made them potential candidate for magnetoelectric devices. (The results of this chapter have been published in Journal of Mater Sci: Mater Electron 31 (2020) 12226–12237 (IF: 2.22)). xiv Chapter 7 is focused on the multiferroic magnetoelectric composites of NdMnO3-BaTiO3 (NMO - BT). The structural investigations revealed the evolution and co-existence of orthorhombic structure of NMO and tetragonal structure of BT in NMO-BT composites and confirm lattice stabilization in terms of symmetry. The dielectric measurements revealed step-like decrease in frequency dependent dielectric constant which confirmed improved conduction nature in NMO-BT composites. The addition of BT phase in NMO improved the remnant magnetization and saturated ferroelectric polarization owing from lattice stability establishing multiferroism in NMO-BT system. The impedance and conductivity measurements confirmed non-Debye type thermally activated conduction behavior and hopping assisted mechanism dominating in NMO-BT composites. The 0.8NMO - 0.2BT composite displayed an enhanced energy storage density of 1.544 mJ/cm3 with an improved efficiency of 50.4 %. The highest value of magnetoelectric coupling obtained was 22 mV/cm/Oe at a field of 5000 Oersted for 0.8NMO-0.2BT composite. The enhancement in energy storage efficiency of 0.8NMO-0.2BT composite and improved magnetoelectric coupling validates its potential for energy storage devices. (The results of this chapter have been communicated to Journal of Alloys and Compounds (IF: 4.65)). Chapter 8 includes summary of the research work described in the previous chapters for optimization of efficient lead free ferroelectric BaTiO3 based magnetoelectric composites for energy storage applications and outlines the future scope of this work.

This thesis project examines Philip Pullman’s controversial trilogy, His Dark Materials (1995-2000), and its relationships in theme and content to John Milton's Paradise Lost (1667). Though Pullman has publicly discussed the influences of Paradise Lost on his trilogy, very little academic work has been published examining the similarities and differences between the two. Specifically, I analyze the paradigms of gender, family, and authority as they are represented by each text. I contrast Pullman's Lyra to Milton's Eve, drawing conclusions about the inherent meanings and differences in the two female protagonists and, consequently, the narrative worlds surrounding them. References cited include works examining His Dark Materials, Paradise Lost, and children's literature.

The multiferroics are an important class of multifunctional material which simultaneously possess spontaneous ferroelectric polarization and magnetic ordering. If there exists a coupling between the ferroelectricity and the magnetic ordering, the materials are known as magneto electric (ME) multiferroic materials. The coupling between the magnetic and electric order parameters allows to tune the magnetic properties by an electric field and vice versa. Multiferroic materials are promising candidate for designing new spintronic devices, advanced sensors, high density ferroelectric memory devices and the emerging category of four-state memory devices. In multiferroic memory devices, data can be written electrically using its ferroelectric property and can be read magnetically without causing any Joule heating. Depending on the origin of ferroelectricity and magnetic orderings, multiferroics can be divided into two categories: type I and type II multiferroics. The type I multiferroics have different sources of ferroelectricity and magnetism. On the other hand, ferroelectricity is induced by the magnetic ordering in type II multiferroic materials and they have a strong ME coupling. However, even after extensive investigations into different families of compounds, a multiferroic material with high-enough polarization and magnetization suitable for practical applications has not been realized yet. In order to overcome this problem, composite multiferroics are designed by combining a ferroelectric and a ferromagnetic material. Recently composite multiferroics have drawn significant attention due to its enormous design flexibility which can be used for a wide range of applications. In this thesis, a thorough study of the structural, electrical, and magnetic properties of multiferroic BiFeO3 and CuO epitaxial thin films is carried out. BiFeO3 is a type I multiferroic material with a perovskite distorted rhombohedral (R3c) crystal structure. It is ferroelectric (TC = 1123 K) and G-type antiferromagnetic (TN = 643 K) at room temperature. Antiferromagnetism in BiFeO3 arises from the Fe sublattice having d5 configuration whereas ferroelectricity appears due to the directional orientation of 6s lone pair electrons of the Bi3+ ion. We observed that the crystal structure of BiFeO3 thin film gets altered depending on lattice misfit stress caused by the substrate which in turn modifies its magnetic properties through strong magneto-structural coupling. Furthermore, a signature of magneto-(di)electric coupling and exchange bias effect were observed between the BiFeO3 and SrRuO3 layers of a heterostructure. On the other hand, CuO is a type II multiferroic material where ferroelectricity is generated between 213 K and 230 K due to incommensurate spiral magnetic spin ordering along its crystallographic ‘b’ axis. We found that CuO thin films can be grown in the direction of its static polarization axis by proper choice of substrate and the temperature dependent magnetic properties of CuO thin films vary depending on its crystallographic orientations due to strong magneto-structural coupling. Chapter 1 provides a general introduction to various physical phenomena, such as ferroelectricity, ferromagnetism, antiferromagnetism, multiferroicity, magneto-electric coupling, and different magnetic interactions, like Dzyaloshinskii-Moriya interaction, and exchange bias effect. Basic concepts of impedance spectroscopy, dielectrics and perovskite structures are also discussed. General introductions of different materials, which are studied in the thesis, and the motivation of choosing them are incorporated at the end of the chapter. Chapter 2 contains the description of thin film growth technique and different steps of device fabrication process. Different characterization techniques, the instruments used for the characterizations and the working-principle of those instruments have been summarized in the chapter. Chapter 3 focuses on the variation of magnetic properties and crystal structure with the thickness of BiFeO3 thin films. BiFeO3 thin films of different thicknesses, ranging from 16 nm to 60 nm, were grown on (001) SrTiO3 substrate by PLD technique. Detailed x-ray diffraction studies show that the 16 nm, 20 nm and 30 nm films have “R-like” crystallographic phase with an out-of-plane lattice parameter of 4.06 Å whereas the 45 nm and 60 nm films have “R-like” and ‘T-like” crystallographic phases simultaneously. The “T-like” phase has an out-of-plane lattice parameter of 4.65 Å and a c/a ratio of 1.25, resembling a tetragonal crystal structure. Off-specular reciprocal space mapping and azimuthal φ scan show that the “T-like” phase deviates from an ideal tetragonal crystal structure by a monoclinic tilt. The occurrence of the “T-like” phase is associated with the formation of a very thin layer of parasitic Bi2O3 phase which appears in between two film-thicknesses of 30 nm and 45 nm and BiFeO3 grows in “T-like” phase thereafter. High lattice mismatch between Bi2O3 phase and BiFeO3 phase causes more distorted unit cell in “T-like” phase with a high c/a ration. Parasitic Bi2O3 phase appears because of slightly higher partial oxygen pressure used during the growth which prevents the formation of the parasitic ferrimagnetic γFe2O3 phase in the films. Moreover, our XPS studies confirmed that the films contain Fe3+ only without any trace of Fe2+ within a resolution of few atomic percentages and the magnetic signals measured in our experiments are entirely from the BiFeO3 phase. The saturation magnetizations of the films were found to increase with decreasing thickness. At room temperature, the saturation magnetization of a 16 nm-thick BiFeO3 thin film is 87 emu/cc but it goes down to 9 emu/cc when the thickness increases to 60 nm. Moreover, it was observed that the 16 nm thick film is magnetically more anisotropic in comparison to the 60 nm thick film and there is an apparent out-of-plane magnetic hard axis in the 16 nm film. Summarizing the results obtained from the films with different thicknesses, it can be concluded that the vanishing magnetic anisotropy is related to the structural transformation of the film. Chapter 4 provides a detailed study of the variation of magnetic properties of a BiFeO3 thin film with its crystal structure. BiFeO3 thin films of different thicknesses were grown on orthorhombic (001) NdGaO3 substrate. In-depth x-ray diffraction studies and off-specular reciprocal space mapping show that a 15 nm thick BiFeO3 film grows with monoclinic crystal symmetry (Cm) with an out-of-plane lattice parameter of 4.187 Å on the NdGaO3 substrate. The crystal structure was further verified by the TEM studies which showed a good agreement with the results obtained from x-ray diffraction studies. To probe the ferroelectric nature of the monoclinic BiFeO3 film, piezo response force microscopy was performed. It was found that the oppositely oriented ferroelectric domains have 180° phase contrast and a phase vs. voltage hysteresis loop gets generated when the domains are switched between two antiparallel directions. DC magnetic measurements at room temperature showed that the saturation magnetization of the 15 nm film with Cm crystal symmetry is as high as ~250 emu/cc. Experimental evidence confirmed that the films are free from all magnetic parasitic phases and the high saturation magnetization comes solely from the BiFeO3 phase. For comparative study, BiFeO3 films of similar thickness were deposited on (001) SrTiO3 under identical conditions which grew in “R-like” crystal structures. We saw that “R-like” BiFeO3 films have saturation magnetization 2.5 times lower (~100 emu/cc) than that of the film with Cm structure grown on NdGaO3. Our observation was further supported by density functional theory calculations which show that BiFeO3 has a ferromagnetic ground state in the Cm crystal phase. The theoretically obtained magnetic moment is 266 emu/cc which is very close to magnetization values found experimentally. Chapter 5 deals with the magnetic interaction and the magneto-electric coupling between the BiFeO3 and SrRuO3 layers of a heterostructure. BiFeO3/SrRuO3 heterostructures were grown on (001) SrTiO3 substrate by PLD technique. The ferroelectric nature of the top BiFeO3 layer was probed by out-of-plane piezo response force microscopy technique. Temperature dependent magnetization measurements of the heterostructure show a sharp ferromagnetic to paramagnetic transition at 160 K which arises from the bottom SrRuO3 layer. Therefore, the heterostructure is ferroelectric and ferromagnetic below 160 K. Magnetic interactions between the two layers were investigated by isothermal magnetic hysteresis loop (M-H) measurement in a SQUID magnetometer. The M-H measurements at 10 K showed a two-step magnetic hysteresis loop which implies that magnetic moments of the SrRuO3 layer get pinned by the magnetic interaction between the two layers. During magnetization reversal process, the pinned magnetic moments switch at a higher magnetic field and generate the second step of the hysteresis loop whereas the first step appears at a lower magnetic field during the switching of the free SrRuO3 moments. The amount of the pinned SrRuO3 moments depends on the thickness of the BiFeO3 layer as the magnetic properties of a BiFeO3 thin film are related to its thickness. Moreover, evidence of the exchange bias effect was also found in the heterostructure. Field-cooled M-H measurement shows that the second step of the hysteresis loop shifts in two opposite directions along the magnetic field axis depending on the polarity of the cooling field whereas the first step doesn’t respond to the cooling field. This confirms that the exchange bias effect is directly related to the pinned magnetic moments of the SrRuO3 layer. The total amount of pinned moment and hence the exchange bias effect reduces with increasing temperature and disappears completely above 100 K. A strong coupling between the electrical properties of the BiFeO3 layer and the magnetic properties of the SrRuO3 layer was also observed in the heterostructure. To carry out electrical measurements, interdigitated gold electrodes were fabricated on the BiFeO3 layer of the heterostructure by standard photolithography, magnetron sputtering, and lift-off procedure. Temperature dependent resistance and reactance measurements of the heterostructure at different frequencies show anomalies at ferromagnetic TC of the bottom SrRuO3 layer. Moreover, temperature dependent capacitance measurement at 0 T and at 5 T magnetic fields also showed anomalies near 160 K which indicate that the electrical properties of the heterostructure are affected by the magnetic transition of the SrRuO3 layer. Furthermore, impedance spectroscopy measurements were carried out at different constant temperatures and the corresponding Nyquist plots were fitted with an equivalent circuit model. Remarkably, the capacitance and resistance of the equivalent circuit corresponding to the BiFeO3 layer of the heterostructure, show anomalies at 160 K. Absence of any dielectric anomaly at 160 K in pure BiFeO3 confirms that the observed ones appear because of the magnetic phase transition of the bottom SrRuO3 layer. Therefore, the BiFeO3/SrRuO3 heterostructure has ferroelectric and ferromagnetic properties along with a strong magneto-electric coupling between the layers which can be a promising candidate for the composite multiferroic. Chapter 6 describes a correlation between the crystal structure and magnetic properties of CuO thin film. CuO thin films were grown on (001) SrTiO3, (110) SrTiO3, and (111) Si substrate with MgO buffer layers by PLD technique. On (110) SrTiO3 substrate, CuO thin films grow along [010] direction, which is the direction of ferroelectric polarization of CuO, but growth direction becomes [111] when (001) SrTiO3 substrate is used. The CuO film becomes polycrystalline when it is grown on (111) Si substrate. To find the in-plane epitaxial relations between the substrate and the two layers, cross-sectional TEM of the heterostructure grown on (110) SrTiO3 was carried out. HRTEM images showed very sharp interfaces between the layers indicating high-quality growth of the heterostructure. The epitaxial relations were deduced from the SAED pattern and the FFT pattern of the HRTEM images. Distinctly different temperature dependent magnetic properties were found for three differently oriented CuO films. Two anomalies at 213 K and 230 K are clearly visible in temperature dependent magnetization (M vs. T) plot of the heterostructure with (010) CuO film which are associated with the two magnetic transitions of CuO. On the other hand, no such anomaly was observed in M vs. T plot of the heterostructure with (111) CuO film. The heterostructure with polycrystalline CuO film shows a very weak magnetic anomaly at 230 K in its M vs. T plot. It can be concluded from our studies that the contrasting magnetic behaviours of these three heterostructures are due to the difference in epitaxial orientations of the CuO layers. Moreover, CuO thin films can be successfully grown in the direction of static ferroelectric polarization which is the ‘b’ axis of its monoclinic crystal structure. Chapter 7 concludes with general findings pertaining to various observations made in the different chapters. Prospects for future work are briefly outlined in this chapter.

Tese de doutoramento em Ciências da Engenharia Mecânica (Ciência dos Materiais) apresentada à Fac. de Ciências e Tecnologia da Univ. de Coimbra
A presente dissertação de doutoramento incide sobre a caracterização química e estrutural de filmes finos de W-Me-C (Me=Ti, Cr, Fe, Co, Ni, Pd, Au), obtidos por pulverização catódica, e tem como objectivo principal determinar a influência do elemento Me na estrutura inicial (pós-deposição) dos filmes e avaliar a sua estabilidade com a temperatura. Pretende-se assim conhecer os fenómenos que estão na origem da formação de estruturas metaestáveis do tipo cristalino ou amorfo e contribuir para a determinação das fases estruturais existentes a temperaturas inferiores à temperatura de sinterização dos sistemas W-Me-C. Para tal, recorreu-se a um conjunto variado de técnicas experimentais de análise química e microestrutural, de entre as quais se referem a micro-sonda electrónica (EPMA), a micro-sonda iónica (SIMS), a difracção de raios X (XRD) em baixo ângulo, a microscopia electrónica de transmissão (TEM), a espectrometria de Mössbauer, a espectrometria de absorção de raios X (EXAFS) e a análise térmica diferencial (DTA). Os resultados obtidos neste estudo revelam que a grande maioria dos metais de transição formam com o tungsténio e com o carbono uma estrutura c.f.c. do tipo b-MC1-x (M=W, Me); a amorfização dos filmes W-C ocorre apenas mediante a adição de metais do grupo VIIIA da Tabela Periódica, e é resultado das características físicas e químicas destes elementos. No que se refere à estabilidade dos sistemas W-Me-C com a temperatura, verifica-se que a presença de um metal com elevada afinidade para o carbono (caso do titânio e do crómio) induz um aumento da temperatura de transformação da fase cristalina metaestável b-MC1-x; contrariamente, os sistemas W-Me-C, em que Me é um metal com fraca afinidade para o carbono, evoluem estruturalmente no domínio de temperaturas estudado, tendendo para o estado de equilíbrio. A estabilidade dos filmes cristalinos é superior à dos filmes amorfos.

Dissertação de mestrado integrado em Engenharia de Materiais
Os elétrodos/ sensores de aplicação biomédica podem ser de materiais tão diversos como: metais, silício/dióxido de silício, vidro, entre outros. Contudo, nos últimos tempos tem-se verificado uma crescente utilização dos substratos poliméricos em detrimento dos anteriores por várias razões, sendo talvez as mais importantes: o baixo custo e a fiabilidade que lhes é associada - uma vez que são facilmente configuráveis de acordo com a finalidade a que se destinam e garantem com alguma confiança a estabilidade das medidas efetuadas. Porém, para funcionarem como elétrodos, estes substratos necessitam de ser superficialmente funcionalizados em termos de contacto elétrico. Investigações recentes mostram resultados bastantes promissores na utilização de filmes finos na otimização da interface elétrica de sensores poliméricos. Neste sentido, o trabalho realizado ao longo desta dissertação teve por base a otimização de um conjunto de processos físicos com vista a concretização de um objetivo maior: o da construção de elétrodos/sensores com base polimérica para aplicações biomédicas. Os elétrodos serão construídos a partir de diferentes bases poliméricas, nomeadamente o polipropileno (PP) e o politereftalato de etileno (PET) que posteriormente serão funcionalizadas com filmes finos condutores de Ti-Me (Me = Al, Au) - responsáveis por transmitir e amplificar o sinal recebido pela base polimérica. Na realização deste estudo, várias etapas foram percorridas. Numa primeira fase (Capítulo 3) estudou-se a influência da adição do metal Me, isto é do alumínio (Al) e do ouro (Au) nas caraterísticas fundamentais (composição, morfologia e estrutura cristalina) dos filmes finos produzidos e o modo como essas alterações se refletiram nas propriedades fundamentais (elétricas e mecânicas) dos mesmos. Numa segunda fase (Capítulo 4), procedeu-se à ativação/modificação das superfícies poliméricas através de diferentes tratamentos de ativação por plasma, uma vez que são sobejamente conhecidos os problemas de adesão dos revestimentos metálicos quando depositados neste tipo de substratos. As superfícies poliméricas ativadas/funcionalizadas foram alvo de um estudo detalhado, por forma a permitir selecionar o conjunto de condições que melhor parecem promover a funcionalização do polímero, com base no estudo das alterações provocadas à superfície, imediatamente após a realização dos diferentes tratamentos de plasma. Por fim, otimizados os tratamentos de ativação por plasma na superfície dos substratos poliméricos, procedeu-se à produção dos “pré - sensores”, isto é, os filmes finos de Ti-Me (Me = Al, Au) foram depositados nos substratos poliméricos para poderem ser testados em termos de algumas das suas propriedades físicas fundamentais. As alterações das caraterísticas superficiais foram detalhadamente estudadas e a resposta mecânica e elétrica do compósito: base polimérica + filme fino foi aferida por ensaios de tração e medidas de resistência elétrica em função da deformação produzida.
Several materials can be used to fabricate sensores devices, such as: metals, silicon/silicon dioxide, glass, among others. However, in nowadays the polymeric substrates are often used, rather than the conventional substrates, for many reasons being perhaps the low cost and the versatility the most important ones. The polimeric substrates can be easily handled according to the intended purpose ensuring with some degree of certainty the accuracy of the performed measures. However, if this kind of material is to be used as electrodes, superficial functionalization in terms of electric contact should be performed. Indeed, recent studies show many promising results when thin films were used to optimize the electric interface of polymericbased sensors. Therefore, the main purpose of the work developed during this dissertation was based in the optimization of a set of physical plasma processes aiming the activation/functionalization of polymeric-based surfaces in order to obtain electrodes/sensors for biomedical applications. Two very different kinds of polymers were chosen to provide the bases for the electrodes: polypropylene (PP) and polyethylene terephthalate (PET) further functionalized with intermetallic thin films of Ti- Me (Me = Al, Au), which the main responsability is the transmission and amplification of the signal received by the polymers, when operating. The present work is organized in three main chapters: the first one (Chapter 3) is dedicated to study the influence of the metal addition (aluminum and gold) into the titanium matrix, based on the films characterization (composition, morphology and crystalline structure) as a function of the Me/Ti ratio. The changes promoted in the main functional properties of the coatings (electrical and mechanical) were also studied. The chapter 4, is dedicated to the activation/functionalization of the polymeric surfaces due to the problems of adhesion between metallic thin films and polymeric substrates. Several treatments were performed and the modified surfaces of the two polymers (PET and PP) submitted to a detailed study in order to understand the modifications occurred on their surface. The main goal is reach the best conditions of plasma treatments that better promote the films adhesion. Finally, the chapter 5 is dedicated to the sputtering depositions of the Ti-Me thin films onto the polymeric substrates, taking into account the informations obtained in the previous chapters.The changes promoted in the superficial features were studied in detail. Moreover, the mechanical and electrical response of the composite: polymer + thin film was measured by traction tests and electrical resistivity measurements as a function of the deformation produced.

碩士
國立臺灣科技大學
機械工程系
99
Bi2O3-based solid-state electrolyte materials with the best conductivity showed the potential to be applied as electrolyte layer for intermediate temperature solid oxide fuel cells (IT-SOFCs). Investigations reported that doped-Bi2O3 might occur phase transformations during heating or cooling to degrade it ionic conductivity. In order to stabilize the high temperature phase (δ-phase or cubic phase) in room temperature, many reports addressed the possible routes to maintain the conductivity properties in a temperature range. For example, the addition of various alio-valent cationic dopants, such as TiO2, SnO2, ZrO2, TeO2 and Nb2O5, is the one of effective ways to achieve the goal, especially Y2O3 and ErO2 of the famous dopants. However, one of the troublesome problems of Bi2O3-based solid-state electrolyte materials which were reduced in the fuel side to losing it ionic conductivity in the SOFC operating conditions. This study focused on material characteristics and thermochemical stability of TiO2-doped Bi2O3 and ZrO2-doped Bi2O3 solid-state electrolytes, and it divided into two subjects: (1) material characteristics of solid-state electrolyte and (2) thermochemical stability assessment of solid-state electrolyte. In binary system of Bi2O3-TiO2 and Bi2O3-ZrO2, this study was prepared TiO2-doped Bi2O3 slurry by planetary ball milling, and then used vacuum evaporator to obtain the starting powder. After calcining and sintering in the air, XRD results indicated lattice constants of the prepared powder of Bi2O3 increased at a-axis and c-axis as the dopant of TiO2. The sintering sample showed relatively high density (> 95.0% T.D.) by Archimedes method. Electrical behaviors were measured by two-probe DC method in air. As sintering at 770°C for 2hrs, the highest total conductivities were obtained in 1 mol% doped Bi2O3 (1BTO) with σ600℃=9.00×10-4 Scm-1, but the result was still lower than YSZ. In thermochemical stability measurement, redox reaction of the prepared electrolyte was carried by TGA measurement under CH4 and H2 atmosphere, respectively. The 14BTO represented the best stability under CH4 atmosphere compared with Bi2O3 and 14BZO. However, Bi2O3-based solid electrolyte occurred fast reducible reaction in H2 atmosphere. In addition, after redox reaction of 14BZO, XRD results indicated the Bi7.38Zr0.62O12.31 was metastable phase.

碩士
國立臺灣大學
材料科學與工程學研究所
106
This study adapts a melt extrusion module [1, 2], which was designed and developed by our group, selects Cu-base alloys capable of melting at <1300 oC, and has conducted 3D printing to make smart mold in previous study. Therefore, this research objectives are to investigate the hardness, wear resistance and compositional uniformity of Cu-based alloys, and the forces required for the melt extrusion. The results show that the hardness (269 HV) of annealed Cu-9Ni-6Sn is obviously superior to Cu-6Ni-2Al (237 HV) and the surface hardness (207 HV) of Ni-coated key. In contact wear, the higher the hardness of the alloys, the lower the wear rate. The relationship between hardness and wear rate is inversely linear behavior. A quantification analysis of the chemical composition of the wires used for 3D printing used Energy-dispersive X-ray spectroscopy (EDS) for the analysis. The standard deviation for the Ni in Cu-11Ni test is less than 0.2 %. Finally, the melting extrusion simulation of high temperature melt Cu alloy is conducted with 0.4 ~ 0.2 mm nozzle size. The required 4 forces against the frictions coming from the tube wall and the nozzle were considered. The simulation results resolve the flowing behavior of high viscous glass and melt Cu-alloy in Al2O3 nozzle through smaller nozzles.

碩士
國立臺灣大學
材料科學與工程學研究所
103
This study used Cu-based materials as an anode of solid oxide fuel cells (SOFCs) and conducted the following R&D works. Properties of Cu and Cu-Zn alloy were investigated, including electrical conductivity, coefficient of thermal expansion (CTE), hardness and oxidation behavior. The oxidation-resistance of Cu, Ni and Ti-6Al-4V was investigated and compared. Moreover, the microstructure of the oxide layers was observed to verify the results of TGA test. This study also developed cobalt-doped SDC cermet as an electrolyte for intermediate temperature (IT)-SOFC. The Cu-based electrode provided good electronic conductivity and prevented carbon deposition. The SDC was used as catalyst and ionic conductor. The methods to synthesize SDC and sinter a dense SDC electrolyte were also provided in this study. Maximum power density of the Cu-based SOFC was 112 mW cm-2 at 750 oC. On the other hand, due to a low melting point and good formability of Cu-Zn alloy, it was suitably applied on 3D printing (3DP) technique. As a result, a melt-extrusion (ME) module was designed to print Cu-Zn alloy. The ME module could reach 1100 oC to extrude Cu-Zn alloy. Besides, the heat insulation of the module was excellent, which was 51 oC outside the module while the temperature in the nozzle was 1000 oC.

In two essays I investigate two antecedents of self-concept change in consumers: Threats to the self and the activated self-construal and its effect on goal conflict resolution. In the first essay, I explore identity strictly as consumers define themselves in terms of the possessions with which they associate. I argue that ironically the very effort to maintain self-consistency through living up to the value of materialism after facing a mortality salience threat can actually undermine consistency on the level of the extended self of highly materialistic consumers. Specifically, when faced with a mortality salience threat, the consistency of highly materialistic consumers self-concept is disrupted in which they not only detach from formerly intrinsic possessions, but also make formerly extrinsic possessions a more central part of the extended self-concept. I further argue that consumers can be protected from a disruption to self-concept consistency through the process of self-affirmation. In the second essay, I explore how the activated self-construal impacts whether consumers maximize pleasure or engage in self-presentational behavior after they have been invited to choose a gift for themselves. I demonstrate that consumers with an independent (interdependent) self-construal make more indulgent (modest) gift choices for themselves, and that this effect is driven by the activation of a goal to maximize pleasure (behave normatively appropriate). I also identify a boundary condition: When consumers are able to satisfy their activated goal before selecting a gift, the effects cease to exist.
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