Τα Νανοσύνθετα συστήματα πολυμερικής μήτρας – σιδηροηλεκτρικών ή πιεζοηλεκτρικών σωματιδίων (κεραμικά εγκλείσματα) αναμένεται να αποτελέσουν μια νέα γενιά υψηλού τεχνολογικού ενδιαφέροντος που θα επιδεικνύουν λειτουργικές ιδιότητες λόγω της ποικίλης πόλωσης των κεραμικών νανοσωματιδίων. Η διασπορά κεραμικών εγκλεισμάτων στο εσωτερικό πολυμερικής μήτρας προσδίδει στα σύνθετα συστήματα βελτιωμένη μηχανική και ηλεκτρική συμπεριφορά. Τέτοιου τύπου συστήματα υλικών, που έχουν υψηλή ηλεκτρική διαπερατότητα (high-Κ materials) χρησιμοποιούνται σε ηλεκτρονικές εφαρμογές, καθώς μειώνουν τα ρεύματα διαρροής και παράλληλα λειτουργούν ως ενσωματωμένοι νανο-πυκνωτές και αισθητήρες ακουστικών εκπομπών. Η ηλεκτρική απόκριση τους, εκφράζεται κυρίως μέσω της ηλεκτρικής διαπερατότητας και μπορεί να ρυθμιστεί, ελέγχοντας τον τύπο, το μέγεθος και την ποσότητα της κεραμικής ενίσχυσης. Η ενσωμάτωση σιδηροηλεκτρικών ή πιεζοηλεκτρικών κρυστάλλων, που επιδεικνύουν υψηλή πόλωση, σε μια πολυμερική μήτρα, όπως η εποξειδική ρητίνη – που εν γένει είναι ηλεκτρικός μονωτής- με χαμηλή ηλεκτρική διαπερατότητα και υψηλή διηλεκτρική αντοχή μπορεί να οδηγήσει στην ανάπτυξη ενός ευφυούς συστήματος. Σκοπός αυτής της εργασίας είναι η παρασκευή και ο χαρακτηρισμός σύνθετων πολυμερικών συστημάτων εποξειδικής ρητίνης – νανοσωματιδίων τιτανικού ψευδάργυρου (ZnTiO3) καθώς και σύνθετων υβριδικών συστημάτων εποξειδικής ρητίνης - νανοσωματιδίων τιτανικού ψευδάργυρου (ZnTiO3) και τιτανικού βαρίου (BaTiO3) ώστε να οδηγηθούμε σε ένα σύστημα υλικών με βέλτιστη συμπεριφορά. Στο θεωρητικό κομμάτι αυτής της εργασίας συζητούνται βασικές έννοιες και θεωρίες που αφορούν τα σύνθετα υλικά, τη θεωρία των διηλεκτρικών και ενεργών διηλεκτρικών, την ηλεκτρική συμπεριφορά σύνθετων υλικών με πολυμερική μήτρα καθώς και πειραματικές τεχνικές χαρακτηρισμού. Στο πειραματικό μέρος, νανοσύνθετα πολυμερικά συστήματα παρασκευάστηκαν από εποξειδική ρητίνη και νανοσωματίδια ZnTiO3 και BaTiO3. Η μέση διάμετρος σωματιδίων βάσει των προδιαγραφών του προμηθευτή ήταν λιγότερο από 100nm για το ZnTiO3 και στην περιοχή των 30 - 50nm για το BaTiO3. Στη συνέχεια τα νανοσύνθετα υποβλήθηκαν σε μορφολογικό, θερμικό και ηλεκτρικό χαρακτηρισμό. Η μορφολογία των δειγμάτων εξετάστηκε για τυχούσα παρουσία κενών (voids) και συσσωματωμάτων (clusters) μέσω του Ηλεκτρονικού Μικροσκοπίου Σάρωσης (SEM) και η θερμική τους απόκριση μέσω της Διαφορικής Θερμιδομετρίας Σάρωσης (DSC). Η διασπορά των κεραμικών εγκλεισμάτων θεωρήθηκε ικανοποιητική, παρόλο που συνυπάρχουν οι νανοδιασπορές με συσσωματώματα. Οι διηλεκτρικές ιδιότητες και τα σχετιζόμενα φαινόμενα διεργασιών χαλάρωσης μελετήθηκαν με χρήση της Διηλεκτρικής Φασματοσκοπίας Ευρέως Φάσματος (BDS) στο εύρος θερμοκρασιών -100 oC έως 160 oC και στο διάστημα συχνοτήτων 10-1 Hz έως 106 Hz. Η ανάλυση των πειραματικών αποτελεσμάτων διεξήχθη με τη χρήση των φορμαλισμών της ηλεκτρικής διαπερατότητας και του ηλεκτρικού μέτρου. Από τα πειραματικά αποτελέσματα προκύπτει πως παρατηρούνται διηλεκτρικές χαλαρώσεις που οφείλονται τόσο στην πολυμερική μήτρα, όσο και στην ενισχυτική φάση. Τα φάσματα των υβριδικών συστημάτων καταγράφουν τουλάχιστον τέσσερεις διακριτούς τρόπους χαλάρωσης. Αυτά αποδίδονται στη διεπιφανειακή πόλωση (Interfacial Polarization ή φαινόμενο MWS) μήτρας/εγκλεισμάτων, στην α- χαλάρωση λόγω υαλώδους μετάβασης του πολυμερούς και στην β- και γ- χαλάρωση εξαιτίας της κίνησης πλευρικών πολικών ομάδων και τοπικής κίνησης μικρών τμημάτων της πολυμερικής αλυσίδας. Η λειτουργικότητα των νανοσύνθετων σχετίζεται με την μεταβολή της πόλωσης, που σχετίζεται ευθέως με το πραγματικό μέρος της ηλεκτρικής διαπερατότητας, την εξάρτηση της ειδικής αγωγιμότητας από την θερμοκρασία και την περιεκτικότητα σε ενισχυτικό μέσο και την δυνατότητα αποθήκευσης ενέργειας. / Nanocomposite systems, which include ferroelectric or piezoelectric particles represent a novel class of materials which are expected to exhibit functional properties because of the varying polarization of the ceramic particles. Dispersing ceramic inclusions within a polymer matrix, results in enhanced mechanical and electrical behavior. Such material systems exhibiting enhanced electrical response are used in electronic applications, for the reduction of leakage currents, as integrated nano- capacitors and as acoustic emission sensors. The electrical response of these composites, namely dielectric permittivity and conductivity can be tailored, by controlling the type, the size and the amount of ceramic inclusions. The ceramic filler could be ferroelectric and/or piezoelectric crystal particles. Their high level of polarization can be combined with a polymer host, like an epoxy resin – which is, in general, electrical insulator – with low dielectric permittivity and high dielectric breakdown strength. This combination could lead in the development of a smart materials’ system. The aims of this work are the preparation and characterization of epoxy resin nanocomposites with embedded zinc titanate (ZnTiO3) and nanoparticles and in tandem hybrid system of epoxy resin– zinc titanate (ZnTiO3) and barium titanate (BaTiO3) nanoparticles. In the first part of this work basic aspects concerning composite materials, dielectric theory, electrical behaviour and characterization techniques of polymer matrix composites are presented. In the experimental part of this study, nanocomposites were prepared by employing commercially available materials such as epoxy resin, ceramic ZnTiO3 and BaTiO3 nanopowder. The mean particle diameter, as indicated by the supplier, was less than 100nm for ZnTiO3 and 30-50nm for BaTiO3 particles. Furthermore, morphology, thermal and electrical response of the produced specimens was examined. The morphology of the specimens was checked for voids and clusters, by means of Scanning Electron Microscopy and the thermal response via Differential Scanning Calorimetry (DSC). Ceramic particles distribution is considered as satisfactory, although clusters co-exist with nanodispersions in all the examined systems. The dielectric properties and the related relaxation phenomena were studied by means of Broadband Dielectric Spectroscopy (BDS) in the temperature range from -100 oC to 160 oC and frequency range from 10-1 Hz to 10-6 Hz. Experimental data analysis was conducted by means of dielectric permittivity and electric modulus formalisms. Based on the conducted analysis, the recorded relaxation phenomena include contributions from both the polymeric matrix and the reinforcing phase. In the spectra of hybrid nanocomposites at least four relaxation processes can be detected. They were attributed to Interfacial Polarization phenomenon (MWS effect), α-mode due to glass/rubber transition of the polymer and β- , γ- modes resulting from the motion of polar side groups and local motion of small segments of the polymer chain. The functionality of the nanocomposite systems is related to the variation of polarization, which is directly connected to the real part of dielectric permittivity, the dependence of conductivity on the temperature and the filler content, and the energy storage efficiency expressed by the density of energy.

Fundação de Amparo a Pesquisa do Estado de Minas Gerais / In the context of the so-called smart materials, shape memory alloys (SMA) have been extensively investigated aiming at various applications in different types of engineering prob- lems as well as interdisciplinary problems. Specifically, SMAs have been used for the mitiga- tion of mechanical vibrations, owing to their characteristic pseudoelastic effect, which is re- sponsible for the occurrence of hysteresis. Another relevant feature of these materials is the coexistence of two crystallographic phases (martensite and austenite), which have dissimilar mechanical properties, whose relative fractions depend on temperature and stress. In the present dissertation, this latter feature is explored in association with a strategy of passive vibration control which is based on tunable dynamic vibration absorbers (TDVA). These de- vices, once connected to a vibrating structure, can have their inertia and/or stiffness and/or damping adjusted to match the excitation frequency. Specifically, such tuning is achieved by controlling the martensite/austenite fraction by applying convenient thermal loads. By means of numerical simulations, which include the integration of the equations of motion, it is put in evidence the possibility of tuning a TDVA applied to a single degree-of-freedom system, with- in a given frequency band using two configurations of the resilient element (SMA rod and helicoidal spring). The results enable to evaluate the levels of vibration mitigation achieved and confirm that the strategy investigated can provide improved performance in terms of vibration attenuation. / No contexto dos chamados materiais inteligentes, as ligas com memória de forma (Shape Memory Alloys SMA) vêm sendo intensivamente investigadas com vistas a aplicações em diversos tipos de sistemas de engenharia e em problemas interdisciplinares. Especificamente, as SMA têm sido utilizadas para a mitigação de vibrações mecânicas, graças ao chamado efeito pseudoelástico, responsável pela ocorrência de histerese. Outra característica relevante desses materiais é a coexistência de duas fases cristalográficas (martensita e austenita), com propriedades mecânicas distintas, cujas frações relativas dependem da temperatura e da tensão. No presente trabalho, esta última característica é explorada em associação com uma estratégia de controle passivo de vibrações, baseada nos chamados absorvedores dinâmicos de vibrações sintonizáveis (ADV), que são dispositivos conectados à estrutura vibratória, cuja rigidez e/ou inércia podem ser ajustados em conformidade com a frequência de excitação, de modo que a vibração da estrutura seja altenuada. Especificamente, explora-se a possibilidade de confecção de ADVs sintonizáveis cuja rigidez pode ser ajustada por meio de variações controladas da fração relativa martensita/austenita induzidas por alterações da temperatura. Por meio de simulações numéricas, evidencia-se a possibilidade de sintonizar um ADV aplicado a um sistema vibratório de um grau de liberdade, dentro de uma dada faixa de valores de frequência, utilizando duas configurações do elemento resiliente (barra e mola helicoidal de SMA), e quantificam-se as reduções de amplitudes obtidas. Os resultados das simulações confirmam o aumento da eficiência na atenuação de vibrações proporcionado pela estratégia empregada. / Mestre em Engenharia Mecânica

Les multicouches de polyélectrolytes, systèmes auto-assemblés par adsorptions successives de polycations et polyanions, peinent à trouver des applications concrètes en raison de leur fragilité mécanique et du temps nécessaire à leur assemblage. Pour améliorer leur tenue mécanique, nous avons développé une méthode d'assemblage couche-par-couche par liaisons covalentes de films polymères. Des films formés de polymères portant des groupements alcynes et azides ont ainsi été réticulés par une réaction click catalysée par les ions Cu+ obtenus par voie électrochimique. Pour améliorer le mode d'assemblage, l'auto-construction en une seule étape de films par approche morphogénique, a été développée. Cette approche, confinée à la surface et caractérisée par la présence en solution de l'ensemble des constituants, marque une rupture. Elle permet ainsi un contrôle spatial de l'assemblage des films et la combinaison de plusieurs modes d'interactions pendant leur assemblage. Des films dont la cohésion repose sur des interactions covalentes, hôtes-invités et supramoléculaires, ont ainsi été assemblés. L'introduction de nanoparticules métalliques dans les films (multicouches et auto-construits) a également été effectuée dans le but de développer des électrodes de grande surface spécifique. / Polyelectrolyte multilayer films, built by alternated adsorption of polycations and polyanions, face two main challenges: their construction process is tedious and their mechanical stability is poor. We developped a layer-by-layer strategy to improve the film stability by covalent reticulation of the polymers chains by click chemistry. Polymers bearing alkyne and azide functions were reticulated by triggering electrochemically the production of Cu+ catalyst ions. A one pot morphogen driven self-construction strategy was also developped to improve the buildup process of the films.In this case, all the constituants are simultaneously present in solution while the film grows up only at the electrode. Films based on covalent, host-guest and supramolecular interactions were obtained and the possibility of combining different interactions was also demonstrated. Nanoparticles were also included in layer-by-layer and self-constructed films in order to improve the electrode specific area.

Hold down release mechanisms (HDRMs) are used for tightly attaching segments of bodies together when it is desired to release them rapidly at some point. When transporting sensitive payloads on launch vehicles, the challenge arises of releasing the fastened segments of the spacecraft without risking damage to the costly equipment. Non-explosive HDRMs are favourable from a safety perspective as there is a lower risk of producing potentially destructive shock-waves throughout the structure.  One variant of a non-explosive HDRM uses a so called 'split spool initiator'. This initiator can only be used once in the actuator mechanism and to reuse the HDRM the initiator must be replaced. The purpose of this thesis is to design an improved split spool initiator which can be reusable while conserving the functionality aspects of the existing design. To achieve this, different ideas were considered and ultimately a solution using shape memory alloys (SMAs) was explored. A prototype was constructed to demonstrate the functionality of the design and simulations are done to determine the forces acting on different parts of the mechanism. / Hold down release-mekanismer (HDRM) används för att säkert kunna fästa samman delar av strukturer för att sedan kunna lossa dessa vid rätt tillfälle. När det transporteras känslig last på exempelvis rymdfarkoster uppkommer utmaningen att göra så på ett sätt som inte riskerar att skada den ofta dyra utrustningen. Det finns en mängd olika HDRM, dessa kan delas upp i två typer som är icke explosiva release-mekanismer och pyrotekniska release-mekanismer. Icke explosiva release-mekanismer har en fördel över pyrotekniska som är att de inte producerar potentiellt destruktiva chock-vågor som sprids genom strukturen. En typ av icke-explosiva release-mekanismer är den så kallade split spool-initieraren. Denna kan endast användas en gång när fästelementet är aktiverat och för att kunna använda fästelementet igen måste hela initieraren bytas ut. Syftet med denna studie har varit att att designa en förbättrad split spool-initierare som är återanvändbar, medan funktionaliteten hos den ursprungliga designen är bevarad. För att åstadkomma detta övervägdes olika idéer och slutligen valdes en lösning som använder minnesmetaller eller Shape memory alloys på engelska (SMA). En prototyp konstruerades för att demonstrera funktionaliteten hos designen. Simuleringar gjordes även för att bestämma krafter som agerade på split spool-strukturen och för att få en överblick över spänningsfördelningen genom initieraren.

Stoichiometric polyelectrolyte-surfactant complexes represent a type of comb-shaped polymers, in which every polymer chain unit has an electrostatically bound "side chain". These complexes are water-insoluble. In the solid state they assemble spontaneously into mesogenic structures. The [X,Y]-ionenes ([(CH2)XN+(CH3)2(CH2)YN+(CH3)2]nBr-2n) investigated formed stoichiometric complexes with alkyl sulfates. The ionene alkyl sulfate complexes display mesogenicity, i.e. optically isotropic dry complexes underwent lyotropic and thermotropic phase transitions to the optically anisotropic phase (and vice versa) under controlled relative humidity. The optically anisotropic phases exhibited hexagonal textures as revealed by polarizing microscopy. A new feature is the lyotropic transition brought about by the uptake of water through the gas phase. The complexes were all sensitive to both humidity and temperature. In principle, the effects can be applied to measure humidity.

The integration of shape memory alloys (SMAs) into textile-reinforced composites produces a class of smart materials whose shape can be actively influenced. In this paper, Ni-Ti SMA wires are inserted during the weaving of a glass fiber reinforcement textile. This ‘‘active’’ reinforcement is then combined with an elastomeric matrix to produce a highly flexible composite sheet, which maintains high rigidity in the longitudinal direction. By activating the SMAs, high deflection ratios of up to 35% (relative to the component’s length) are achieved. To adjust the composite’s deflection to defined values, a closed-loop control is set up to adjust the current flow through the SMA wires. A control algorithm is designed and evaluated for several test cases. The high deformability and the controllable behavior show the high potential of these materials for applications such as aerodynamic flow control, automation and architecture.

No description available.

Future robotic systems will be pervasive technologies operating autonomously in unknown spaces that are shared with humans. Such complex interactions make it compulsory for them to be lightweight, soft, and efficient in a way to guarantee safety, robustness and long-term operation. This set of qualities can be achieved using soft multipurpose systems that combine, integrate and commute between conventional electromechanical and fluidic drives, as well as harvest energy during inactive actuation phases for increased energy efficiency. Recent research work has shown that dielectric fluids with specific properties, can be combined with stretchable or flexible shell structures made of polymeric dielectric/electrode composite films, to implement a novel type of soft electrically-driven fluidic transducers with self-healing and self-sensing capabilities that take the name of Liquid-based Electro-Active Polymer transducers (LEAPs). These devices are similar to dielectric elastomer transducers in regards to their electrostatic working principle, but they can potentially produce larger displacements due to their lower mechanical stiffness. In this thesis a novel electrostatic transducer is presented; the transducer is made of thin polymer films and liquid dielectrics, combined with rigid stiffening elements to form a circular electrostatic bellow muscle (EBM) unit capable of out-of-plane contraction. These units are easy to manufacture and can be arranged in arrays and stacks that can be employed as contractile artificial muscles, pumps for fluid-driven soft robots, or as energy harvesters. As artificial muscles, EBMs of 20 - 40 millimeters in diameter can exert forces of up to 6 newtons, lift loads over a hundred times their own weight, and reach contractions of over 40 per cent with strain rates over 1200 per cents per second, with a bandwidth over 10 Hz. As pump drivers, EBMs produce flow rates of up 0.63 liters per minute and maximum pressure head of 6 kilopascals, whereas as generators, they reach a conversion efficiency close to 20 per cent. The compact shape, low cost, simple assembling procedure, high reliability and large contractions make the EBM a promising technology for high-performance robotic systems.

Shape memory alloys (SMAs) have been recognized as one of the most promising materials for MEMS micro-actuator applications. Among the available materials, Nickel/Titanium (NiTi) SMAs are more popular because, they exhibit unique properties in shape memory effect (SME) and pseudo-elasticity (PE). In addition NiTi SMA possesses high corrosion resistance, excellent mechanical properties and is also bio¬compatible. NiTi thin-film SMAs have been considered as the most significant material in the field of MEMS applications, which can be patterned with standard lithographic techniques to scale-up for batch production. However, the lack of proper understanding of basic materials’ properties and inability to reproduce, has limited the usage of this material in MEMS devices. The properties of NiTi SMA thin-films are very much sensitive to the elemental composition and structure, which are in turn decided by the deposition process and process parameters. A brief history of NiTi shape memory alloys (SMAs), basic information, transformation characteristics, crystal structure, phase diagram and literature reviewed for the current motivation have been presented in the second chapter In the third chapter, a brief summary about the deposition techniques relevant to NiTi film deposition has been presented. The deposition of NiTi films by a number of deposition techniques such as thermal evaporation, co-evaporation, molecular beam Epitaxy, pulsed laser deposition, flash evaporation, electron beam deposition, filtered arc deposition, ion beam assisted sputter deposition, vacuum plasma spraying, ion beam sputtering, ECR sputtering and magnetron sputtering techniques have been discussed. In order to achieve a precise control over film thickness and composition of the films on to the substrates, the selection of magnetron sputtering has been highlighted. In the present thesis, two prolonged approaches such as DC magnetron sputtering of an alloy target and co-sputtering of elemental targets have been presented. Various characterization techniques used for film thickness, composition, structure, micro¬structure, electrical, phase transformation and mechanical properties have also been briefly presented in the same chapter. In the fourth chapter, description of Conventional Alloy Target Sputtering System has been presented. DC magnetron sputtering of an alloy target with two different atomic ratios (Ni:Ti = 45:55 & 50:50) has been used for depositing the coatings. Several limitations in the reproducibility and repeatability have been observed with single alloy target sputtering, irrespective of the target composition ratio. In addition to this, incorporation of oxygen in the films during and after deposition has been observed, which has limited the extensive usage of this single alloy target system. The limitations regarding control over composition, thickness uniformity over large area have been improved by designing and fabricating a dedicated Three Target Magnetron Co-sputtering System. The vacuum diagnosis of the system under different conditions has been carried out by using PPR-200 Residual Gas Analyzer (RGA), which have included in Appendix I. Similar to alloy target sputtering system, the thickness uniformity and required composition with deposition parameters over a size of 75 mm diameter has been achieved and the process repeatability has been established. Oxygen incorporation in the films during deposition has been minimized by pre-sputtering of Ti target for known duration of time, which has resulted in significant reduction in partial pressure of oxygen in the chamber. The oxide layer formation on film surface has been eliminated by in-situ capping layer (TiN) deposition. In the fifth chapter, the influence of process parameters such as sample locations, substrate to target distance (STD), working pressure (WP), gas flow rates, deposition rates, deposition and annealing temperature, Target power, on the film thickness and composition uniformity have been presented for alloy target sputtering system as well as for the co-sputtering system. The film thicknesses have been measured with stylus method. Film compositions have been determined by energy dispersive X-ray spectroscopy (EDS), Secondary ion mass spectrometry (SIMS), Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS). The working pressure of 1.5 X 10-3 mbar, STD of 90 mm and target power of 100 W have been found to produce coatings having uniform thickness and composition over the given area for alloy target sputtering system. Similar investigations have been carried out for co-sputtered NiTiCu films. The working pressure of 1.5x 10-3 mbar, at a STD of 90 mm, at a rotational speed of 15 rpm and at target powers of 600, 50 and 12 W for Ti, Ni and Cu respectively, have resulted in the thickness and required composition uniformity over a size of 75 mm diameter substrate and the process repeatability has been established. In the Sixth chapter, the influence of process parameters on film structure and micro-structure on the NiTi/NiTiCu films deposited by a single alloy target and co¬sputtering have been studied by different analytical techniques like XRD, TEM, AFM, SEM etc. Phase transformation temperatures and kind of transformations have been investigated by DSC, Resistivity / Temperature and Stress/ Temperature studies and correlations have been established. The process parameters have been optimized for TiN deposition, which act as the capping layer to protect NiTi films from surface oxidation. The variation in mechanical behavior for the NiTi/ NiTiCu films before and after TiN capping by nano-indentation test have also presented. XRD and TEM studies have shown that the NiTi / NiTiCu films deposited at room temperature to 400o C are amorphous. Post-annealing, at a temperature of 450O C or above resulted in the film crystallization with oxide layer formation at the film surface, which has been confirmed by XRD and XTEM studies. In the case of Ni-rich NiTi films, R-phase diffraction peaks have also been identified in addition to the Austenite / Martensite phase. XRD investigations have shown that Ti-rich NiTi and Ni-rich NiTi films have resulted in precipitate free films. In the case of Ti-rich NiTiCu and Ni-rich NiTiCu films, the variations in Ti/Ni target power has resulted in the formation of NiTi 2 and Ni3Ti precipitates along with their parent Martensite and Austenite phases. When the Cu content is increased in NiTiCu films, an increase in number of Martensite phase diffraction peaks in XRD spectrum has been observed. XTEM studies have confirmed formation of oxide layer, inter-metallic layer and interface layer at higher post annealing temperatures. SEM studies have shown that the films deposited at higher gas flow rate results in the columnar micro-structure. In the context of NiTiCu films, the films deposited at higher Ti target power have shown more compact and tightly packed film micro-structure. AFM studies have shown increase in the average crystallite size and film roughness with post annealing temperature and duration. TiN coating has been used as the capping layer onto NiTi / NiTiCu films. Structural and micro-structural comparison of these films before and after TiN coating has resulted the appearance of (111) TiN peak in all TiN capped films. SEM and AFM studies have shown that the film roughness have decreased after capping layer deposition. DSC thermal cycling used to verify the film crystallization temperature has shown the appearance of exothermic peak in NiTi / NiTiCu films. DSC, Resistivity-temperature, stress-temperature response has been confirmed the transformation temperature and kind of transformations in all the films. Residual stress measurements have shown that the crystalline films exhibited lower bi-axial stress in comparison to the amorphous films. Ti-rich NiTi films have shown single phase transformations (M-A and A-M) whereas two phase transformations (M-R-A and A-R-M) have been observed in Ni-rich NiTi films. Higher deposition / annealing temperature have shown the appearance of distinct phase transformation peaks in resistivity vs. temperature studies. In the case of NiTiCu films, the decrease in film crystallization temperature with increase in the Cu content has been observed. The phase transformation temperature evaluated from second thermal cycle has shown decrease in the width of hysteresis loop with increase in the Cu content in NTC films. Nano-indentation studies have been carried out to evaluate the micro-hardness and modulus values of TiN capped and uncapped NiTi / NiTiCu films. The modulus and hardness uniformity have been confirmed for the different location over a diameter of 75 mm. The modulus and hardness values have increased with increase in the substrate and annealing temperature. Increase in the Cu target power has resulted in the increase in the hardness and modulus values under same deposition conditions. TiN coated NiTi / NiTiCu films have shown larger modulus and hardness values than the uncapped films. In the Seventh chapter, the fabrication process and actuation response for silicon dioxide, Aluminum and NiTi SMA coated micro-cantilevers has been discussed. Various nano-structures such as pyramids, beams and pillars by focused ion beam (FIB) micro-machining have been fabricated. High aspect ratio nano-pillars have been selected for micro-compression testing. In summary, this thesis emphasizes on the fabrication of specific sputtering systems relevant to NiTi film deposition and process parameter optimization for desired film thickness and composition uniformity. DC magnetron sputtering of a NiTi alloy target (50:50 and 45:55 at. %) and co-sputtering of elemental targets (Ni, Ti and Cu) have been presented. These films have been investigated for structural, micro-structural, phase transformation and mechanical properties. In-situ deposition of TiN capping layer, on to NiTi / NiTiCu films has been carried out to reduce the oxygen trapping. The fabrication process and actuation response of micro-cantilevers have been described. The etching characteristics to generate various nano-structures viz. pyramids, beams and pillars by focused ion beam (FIB) micro-machining have been investigated and mechanical testing of selected nano-structures have also been reported.

Smart materials is an active research area devoted to the design of structured materials showingphysical properties that can be modified in response to an external stimulus.This study focuses on the analysis and design of adaptive system for vibroacoustic control. Theresearch investigates the design of a active interface made of piezoelectric transducers arranged ina two-dimensional lattice. Each transducer is individually shunted to an external electric circuitsynthesizing a negative capacitance effect. It allows to control waves propagating inside a structuretaking advantage of the multi-field coupling between the structural plate and the electrical circuitsshunting the piezoelectric patches.The performance of the metacomposite has been evaluated through numerous numerical andexperimental tests. The smart wave-guide has been analyzed by using the Bloch theorem appliedto two-dimensional piezo-elastic systems. Subsequently an optimization procedure has been usedwith the purpose to select the most appropriate set of circuit's parameters.A prototype of the smart waveguide has been manufactured and tested. The results results clearlyshow the filtering and attenuating capabilities of this device.Finally a finite element model of the finite extent smart plate has been considered in order toasses the robustness of the proposed control strategy respect to a modification of the circuit'sparameters, the topology of the active interface and the properties of the controlled plate.A brief review conclude the work delineating which aspects of the design should be modified inorder to obtain a device suitable for industrial applications.