Orientador: Elson Longo / Banca: Maria Aparecida Zaghete Bertochi / Banca: Máximo Siu Li / Banca: Gilberto de Campos Fuzari Junior / Banca: Renata Cristina de Lima / Resumo: Este trabalho teve como meta o preparo e o estudo de compósitos polímero/cerâmica com potencial para aplicação como sensor multifuncional, para ser utilizado, tanto para conversão de energia mecânica em energia elétrica bem como para emissão de luz. Para a preparação desse compósito, diferentes pós cerâmicos de estrutura perovskita puros e dopados, com a terra-rara európio (Eu), foram obtidos via Método dos Precursores Poliméricos. Estes pós foram preparados com o objetivo de estabelecer a otimização das propriedades piezoelétricas e luminescentes. Por outro lado os pós misturados ao polímero poli fluoreto de vinilideno (PVDF), formaram os filmes compósitos. Os resultados obtidos neste trabalho foram divididos em 3 tópicos. No primeiro tópico os materiais cerâmicos de BaZrxTi1-xO3 com (x = 0; 0,05; 0,08; 0,1; 0,25; 0,50; 0,75 e 1) foram obtidos e caracterizados. No segundo tópico foram sintetizadas e analisadas as amostras cerâmicas dopadas com íons Eu; Ba1-yEuyZr0,08Ti0,92O3, Ba1-yEuyTiO3 e Ba1-yEuyZrO3 com (y = 0,005; 0,01; 0,02 e 0,04). No terceiro tópico as cerâmicas de melhores propriedades piezoelétricas formaram compósitos com o polímero PVDF em condições que foram otimizadas. Para a caracterização estrutural foram utilizadas as técnicas de Difratometria de Raios-X e a Espectroscopia Raman. A propriedade ótica foi analisada por Espectroscopia de Reflectância no Ultravioleta e Visível e Fotoluminescência. A morfologia das cerâmicas e a superfície e a distribuição da cerâmica no polímero foram observadas por Microscopia Eletrônica de Varredura de Emissão de Campo. A condutividade elétrica, o coeficiente piezelétrico longitudinal d33 e as curvas de histerese foram as ferramentas utilizadas para análise das propriedades elétricas. Todos os compósitos formados apresentaram as propriedades de piezoeletricidade e de fotoluminescência, portanto, possuem condições para serem aplicados como... / Abstract: This research aimed the preparation and study of polymer/ceramic composites with potential applications as multifunctional sensors, to be used for converting mechanical into electrical energy as well as for light emissions. Different perovskite ceramics powders (pure and doped with europium) were obtained by the Polymeric Precursor Method in order to establish the optimization of piezoelectric and luminescent properties. The composite films were formed by the junction of ceramic powders with poly vinylidene fluoride polymer. The results obtained in this study were divided into three topics. In the first topic ceramic materials BaZrxTi1-xO3 (x = 0, 0.05, 0.08, 0.1, 0.25, 0.50, 0.75 and 1) were obtained and characterized. In the second topic were collated and analyzed the ceramic samples doped with ions Eu3+: Ba1-yEuyZr0,08Ti0,92O3, Ba1-yEuyTiO3, and Ba1- yEuyZrO3 with (y = 0.005, 0.01, 0.02, and 0.04). In the third topic several variables were tested in order to optimize the composites formation using the best conditions. The composites that were obtained in the optimized conditions were analyzed. For structural characterization were used the X-Ray Diffraction and Raman Spectroscopy techniques. The optical property was analyzed by Reflectance Spectroscopy in the UV-Vis range and Photoluminescence measurements. The ceramic surface morphology and the ceramic distribution in the polymer were studied by Scanning Electron Microscopy Field Emission Gun. The electrical conductivity, the longitudinal piezoelectric coefficient d33, and hysteresis curves of these materials were the tools used to analyze their electrical properties. All composites showed the piezoelectricity and the photoluminescence properties and therefore are able to be applied as a multifunctional sensor. / Doutor

Made available in DSpace on 2015-08-20T17:09:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-10-30. Added 1 bitstream(s) on 2015-08-20T17:27:14Z : No. of bitstreams: 1 000747528.pdf: 2389252 bytes, checksum: 155298085bba4cff332ca297d4039de6 (MD5) / Este trabalho teve como meta o preparo e o estudo de compósitos polímero/cerâmica com potencial para aplicação como sensor multifuncional, para ser utilizado, tanto para conversão de energia mecânica em energia elétrica bem como para emissão de luz. Para a preparação desse compósito, diferentes pós cerâmicos de estrutura perovskita puros e dopados, com a terra-rara európio (Eu), foram obtidos via Método dos Precursores Poliméricos. Estes pós foram preparados com o objetivo de estabelecer a otimização das propriedades piezoelétricas e luminescentes. Por outro lado os pós misturados ao polímero poli fluoreto de vinilideno (PVDF), formaram os filmes compósitos. Os resultados obtidos neste trabalho foram divididos em 3 tópicos. No primeiro tópico os materiais cerâmicos de BaZrxTi1-xO3 com (x = 0; 0,05; 0,08; 0,1; 0,25; 0,50; 0,75 e 1) foram obtidos e caracterizados. No segundo tópico foram sintetizadas e analisadas as amostras cerâmicas dopadas com íons Eu; Ba1-yEuyZr0,08Ti0,92O3, Ba1-yEuyTiO3 e Ba1-yEuyZrO3 com (y = 0,005; 0,01; 0,02 e 0,04). No terceiro tópico as cerâmicas de melhores propriedades piezoelétricas formaram compósitos com o polímero PVDF em condições que foram otimizadas. Para a caracterização estrutural foram utilizadas as técnicas de Difratometria de Raios-X e a Espectroscopia Raman. A propriedade ótica foi analisada por Espectroscopia de Reflectância no Ultravioleta e Visível e Fotoluminescência. A morfologia das cerâmicas e a superfície e a distribuição da cerâmica no polímero foram observadas por Microscopia Eletrônica de Varredura de Emissão de Campo. A condutividade elétrica, o coeficiente piezelétrico longitudinal d33 e as curvas de histerese foram as ferramentas utilizadas para análise das propriedades elétricas. Todos os compósitos formados apresentaram as propriedades de piezoeletricidade e de fotoluminescência, portanto, possuem condições para serem aplicados como... / This research aimed the preparation and study of polymer/ceramic composites with potential applications as multifunctional sensors, to be used for converting mechanical into electrical energy as well as for light emissions. Different perovskite ceramics powders (pure and doped with europium) were obtained by the Polymeric Precursor Method in order to establish the optimization of piezoelectric and luminescent properties. The composite films were formed by the junction of ceramic powders with poly vinylidene fluoride polymer. The results obtained in this study were divided into three topics. In the first topic ceramic materials BaZrxTi1-xO3 (x = 0, 0.05, 0.08, 0.1, 0.25, 0.50, 0.75 and 1) were obtained and characterized. In the second topic were collated and analyzed the ceramic samples doped with ions Eu3+: Ba1-yEuyZr0,08Ti0,92O3, Ba1-yEuyTiO3, and Ba1- yEuyZrO3 with (y = 0.005, 0.01, 0.02, and 0.04). In the third topic several variables were tested in order to optimize the composites formation using the best conditions. The composites that were obtained in the optimized conditions were analyzed. For structural characterization were used the X-Ray Diffraction and Raman Spectroscopy techniques. The optical property was analyzed by Reflectance Spectroscopy in the UV-Vis range and Photoluminescence measurements. The ceramic surface morphology and the ceramic distribution in the polymer were studied by Scanning Electron Microscopy Field Emission Gun. The electrical conductivity, the longitudinal piezoelectric coefficient d33, and hysteresis curves of these materials were the tools used to analyze their electrical properties. All composites showed the piezoelectricity and the photoluminescence properties and therefore are able to be applied as a multifunctional sensor.

Piezoprobes of design Phillips-Curzon 1 mm in diameter have been calibrated in the pressure range 0.2 to 35 atm. Step pressure pulses for the calibration were produced with plane shock waves in the range 0.2-1 atm, and with plane detonations in Acetylene-Oxygen in the range 2-35 atm. The calibrated probes were used to measure the space-time pressure profiles in I) concentric detonations II) radiation fronts behind windows and III) pressure waves induced by an intense light source. The measurements supported existing models of the dynamics of these pulsed discharges. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Materials have always had a large impact on society over the different ages. Piezoelectric materials are the often ‘invisible’ materials which find widespread use, unknown to the general public by large. Mobile electronics, automotive systems, medical and industrial systems are few of the key areas where ‘piezoelectricity’ is indispensable. The parking sensor of our car uses the effect and even the echo to image an unborn baby in a womb requires the exploitation of the piezoelectric effect. The work presented in this thesis investigates the piezoelectric effect in semiconductors, namely in III V, III N and II VI materials to have a better understanding and design potential applications in light emitting diodes (LEDs) and other electronic devices. The current work focuses on the non-linear behaviour in the strain of the piezo effect, which is manifested by the generation of electric field under crystal deformation. Previous works have already confirmed the reports of the existence of non-linear piezoelectric effects in zincblende III V semiconductors. Here, the same semiempirical approach using Density Functional Theory has been utilized to investigate the strain dependent elastic and dielectric properties of wurtzite III N materials. While we report the strong non-linear strain induced piezoelectric behaviour with second order coefficients, all spontaneous polarization terms are substantially smaller than the previously proposed values. We show that, unlike existing models, our calculated piezoelectric coefficients and nonlinear model provide a close match to the internal piezoelectric fields of quantum well and superlattice structures. Also, pressure dependence of the piezoelectric field in InGaN based LEDs predicts a significant improvement of the spontaneous emission rate can be achieved as a result of a reduction of the internal field. The LED devices using the proposed structures including a metamorphic layer under the active region of the device are expected to increase their light output power by up to 10%. We also explored the impact of the non-linear piezo effect in nanowires and present a further theoretical computational study of single photon sources optimization in InGaN based wurtzite single quantum dots. We observed the light emission can be made by those single photon sources covering the entire visible spectrum through suitable change in the alloy composition.

No description available.

Since the discovery of stress-generated potentials (SGPs) in bone by Fukada and Yasuda in 1957, researchers have tried to understand their origin and function in the maintenance of bone. There have been a variety of methods attempting to quantify these SGPs in both wet and dry bone. In this study, I prepared both dry and wet beams of cortical bovine bone and subjected them to mechanical deformation in cantilever bending. Mechanical testing was performed to explore how the magnitude of the SGPs was affected by hydration levels, strain, and pressure gradients associated with various load magnitudes and deformation rates. Signals that were collected from the dry bone samples were attributed to motion artifact resulting from the movement of the materials testing machine and load cell. The SGPs from wet bone, on the other hand, consistently produced exponentially decaying signals following deformation that were maintained throughout held deformation and produced an SGP of opposite magnitude upon release of deformation. The exponentially decaying SGP signal produced after application of a step load to wet bone samples was determined to fit a two-term exponential equation (V(t) = Aet/τ1 + Cet/τ2). The first term, made up of the A-coefficient and τ1, was found to be dependent on deformation rate whereas the second term, containing the C-coefficient and τ2, was dependent on load magnitude. The sum of the two coefficients determine the maximum voltage the SGP can reach. Additionally, samples were left to air dry for one hour and tested intermittently throughout that time period. SGP signals diminished significantly over the hour, therefore, it has been concluded that the majority of the SGP signal is due to streaming potentials caused by ionic fluid movement within the bone upon deformation. / Thesis / Master of Applied Science (MASc) / Mechanical deformation of bone produces electrical signals known as stress-generated potentials (SGPs). In this study, I mechanically tested wet beams of bone to assess how the SGPs were affected by hydration levels, load magnitudes, and deformation rates. Dry bone samples did not produce any acceptable SGP signals. The SGPs from wet bone, however, produced repeatable signals that decayed following deformation. With a step load input, the decaying SGP signal fit a two-term exponential equation (V(t) = Aet/τ1 + Cet/τ2). The first term, made up of the A-coefficient and τ1, was found to be dependent on deformation rate whereas the second term, containing the C-coefficient and τ2, was dependent on load magnitude. The two coefficients, the A and C-coefficient, together determine the maximum voltage the SGP can reach. The result of this work showed that SGPs in bone are dependent on tissue hydration and vary with load magnitude and deformation rate.

Current and future space exploration operations rely heavily on space-borne telescopes, of which mirrors are an integral component. However, traditional solid mirrors are heavy and require a big storage space. Deploying membrane mirrors can alleviate many of these obstacles. Membrane mirrors are light and can be compactly stowed resulting in cheap launching costs. It was also demonstrated that membrane mirror would provide quality optical imaging capabilities. However, membrane mirrors exhibit undesirable vibrations that can be caused by thermal gradients or internally-induced excitations. The undesirable vibration degrades the performance of these mirrors. Hence, it is proposed to augment membrane mirrors with smart actuators around their outer rim. Smart actuators can be used to suppress the undesirable vibration. More importantly, such a system provide the capability to form appropriate surfaces to correct for aberrations in an incoming wavefront. In this spirit, this work aims at modeling and control a membrane mirror augmented with smart actuators. The approach here to consider a membrane strip augmented with smart actuators as a prelude for studying circular membranes. We consider strips of membrane material, and treat two such structures: a membrane strip augmented with a single piezoceramic bimorph acting in bending, and a membrane strip augmented with multiple macro-fiber composite bimorphs. The later structure is studied under two actuation configurations. In the first configuration, both actuators act in bending. In the other configuration, one actuator acts in bending and the second acts in tension. The developed models of both structures were validated experimentally. Then, control laws were derived for both structures. An optimal proportional-integral controller is used for the membrane strip augmented with a single piezoceramic bimorph. For the membrane strip augmented with two macro-fiber composite bimorphs, a sliding mode controller with a switching command is used. Simulation results are presented to demonstrate the efficacy of the proposed control laws. Then, a circular membrane augmented with macro-fiber composite bimorph actuators is considered. We derive the governing equation of the structure for the general configuration, where actuators are producing bending moments and radial loading. Then, we seek a reduced order model of the structure. We work on obtaining a Galerkin expansion of the model where the test functions used are the mode shapes of the structure as obtained from a finite element analysis conducted in a commercial software package. Then the control problem is considered. The objective is to correct for optical aberrations, so the Zernike polynomial basis functions are used. A transformation from the optical modes to the mechanical modes is presented and an augmented adaptive controller is used to correct for image aberrations. The results presented show the efficacy of the controller. / Ph. D.

A differential steered, 13.6 kg robot was developed as an intelligent tire testing system and was used to investigate the potential of using piezoelectric film sensors in small tube-type pneumatic tires to characterize tire-ground interaction.<br />One focus of recent research in the tire industry has been on instrumenting tires with sensors to monitor the tire, vehicle, or external environment. On small robots, tire sensors that measure the forces and deflections in the contact patch could be used to improve energy efficiency and/or mobility during a mission.<br />The robot was assembled from a SuperDroid Robots kit and instrumented with low-cost piezoelectric film sensors from Measurement Specialties between the inner tube and the tire.  An unlaminated and a laminated sensor were placed circumferentially along the tread and an unlaminated sensor was placed along the sidewall.  A slip ring transferred the signals from the tire to the robot. There, the signal conditioning circuit extended the time constant of the sensors and filtered electromagnetic interference.  The robot was tested with a controlled power sequence carried out on polished cement, ice, and sand at three power levels, two payload levels, and with two tire sizes.<br />The results suggest that the sensors were capable of detecting normal pressure, deflection, and/or longitudinal strain.  Added payload increased the amplitude of the signals for all sensors.  On the smaller tires, sensors generally recorded a smaller, wider signal on sand compared to cement, indicating the potential to detect contact patch pressure and length.  The signals recorded by the unlaminated sensor along the tread of the smaller tire were lower on ice compared to cement, indicating possible sensitivity to tractive force.  Results were less consistent for the larger tires, possibly due to the large tread pattern. / Master of Science

The manufacturing and characterisation of piezoelectric textile fibres are described in this thesis. A piezoelectric material is one that generates an electric voltage when deformed, a property which exists in a number of materials. The polymer with the strongest known piezoelectric effect today is poly(vinylidene fluoride) (PVDF), however it must be processed under certain conditions to become piezoelectric. This study shows that piezoelectric bicomponent PVDF-based fibres can be produced by melt spinning, which is a common and relatively simple fibre spinning method. The melt spinning process must include cold drawing, as this introduces a polar crystalline structure in the polymer. The fibres must also be electroded, which is done by producing bicomponent fibres with a core-and-sheath structure. The core is electrically conductive and constitutes an inner electrode consisting of a carbon black/polymer compound, whereas the sheath is PVDF and constitutes the piezoelectric component. Being sensitive to both deformation and temperature changes, these fibres are anticipated to be useful in a number of sensor applications. The flexibility and small size of the fibres makes it possible to include them as miniature-sensors in structures or garment without affecting the shape or comfort.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aim of this study was to develop a ZnO nanowire-array biosensor that would detect immunoglobulins and record changes in the concentration of an antibody. Early detection of disease-causing agents is essential for an early response. In contrast to conventional methods, biosensors may detect disease-associated agents much faster and more accurate, which holds specific benefits to rural communities. The development of such a biosensor would be favourable for diagnostics in underprivileged communities without infrastructure. The hypothesis was that binding of antibodies to the surface of ZnO nanowires would result in the generation of a piezoelectric potential that, when channelled through a Schottky barrier, would produce a constant voltage reading. Piezoelectricty would be generated due to the bending of the nanowires, or tensile stress applied to the nanowires due to binding of the antibodies. The performance of such a device largely depends on the methods used to construct the ZnO nanowires and methods used to funtionalize the sensor surface. The biggest challenge was thus to chemically modify the self-assembled monolayers (SAMs) and create intermediate monolayers that would react to primary amino groups of lysozyme and form a covalent amide bond. Lysozyme was selected as model antigen, since its structure and reaction with antibodies has been well studied. Alkanethiol and dialkyl disulphides were used to form SAMs. Different SAMs were compared to select the absorbate that would bind the highest concentration of lysozyme. Lysozyme was best immobilized onto Au film layers in the presence of SAM 3-mercaptopropionic acid. Weakest immobilization was in the presence of combined SAM 11-mercaptoundecanoic acid/1-nonanethiol. The sensitivity of the constructed ZnO nanowire biosensor was tested in vitro, in the presence of different concentrations of lysozyme antibodies. An increase in the dimension of the ZnO seed layer led to an increase in the mean diameter of the ZnO seed grains, and subsequently an increase in the mean diameter of the synthesized ZnO nanowires. Deposition of the ZnO seed layer, using the RF cylindrical magnetron sputtering technique, improved the c-axis alignment of the nanowires and produced nanowires with similar dimensions. However, deposition of the ZnO seed layer using the sol-gel spin coating technique, produced nanowires with irregular c-axis alignments and irregular diameters. An increase in the Au film thickness led to a decrease in the mean diameter of the synthesized ZnO nanowires and worsening of the c-axis alignment. In contrast to single crystalline Au (111) film layers, polycrystalline Au layers increased the mean diameter of the synthesized nanowires. The crystal orientation of the Au film layer had no effect on the c-axis alignment. Increased voltage readings were recorded with an increase in antibody binding, indicating that the ZnO nanosensor may be used to record changes in immunoglobulin levels. Antibody concentrations ranging from 10 ng/ml to 20 μg/ml were sensed. This is the first study showing that ZnO nanowires, conformed into piezoelectric transducers, may be used in the detection of antibodies. The current size of the chip with ZnO nanowires is approximately 1 cm², which is too big to incorporate into a compact monitoring device. Apart from the challenge to produce smaller nanowire-arrays, highly sensitive sensors and miniature amplifiers will have to be developed to increase the strength of the signals generated by the nanowires. The biosensor will also have to be optimised to detect a variety of immunoglobulins. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om ‘n ZnO nanodraad biosensor te ontwikkel wat immunoglobuliene kan opspoor en veranderinge in konsentrasies van die teenliggaampies sal reflekteer. Vroë deteksie van siekte veroorsaakende agente is belangrik vir n vroeg tydige respons. In teenstelling tot konvensionele metodes, kan biosensors siekte veroorsaakende agente vining en akkuraat opspoor, wat veral voordele vir gemeenskappe in landelike gebiede inhou. Die hipotese was dat binding van teenliggaampies aan die ZnO nanodrade ‘n piëzo-elektriese potensiaal sal skep, wat dan ‘n konstante leesbare spanningspotensiaal sal lewer nadat dit deur ‘n Schottky versperring gestuur is. Piëzo-elektrisiteit word gegenereer deur die buiging van die nanodrade, of deur spanning wat op die nanodrade geplaas word deur binding van die teenliggaampies. Die sukses van die ontwerp hang grootliks af van die metode wat gebruik word om die ZnO nanodrade te konstrueer en metodes wat gebruik word om die sensor oppervlak te funksionaliseer. Die grootste uitdaging was dus om die monolae wat outomaties saam groepeer (SAMs) chemies so te verander dat intermediêre monolae vorm wat aan primêre aminogroepe van lisosiem bind ten einde kovalente amied-bindings te vorm. Lisosiem is as model antigeen geselekteer omdat die struktuur en reaksie daarvan met teenliggaampies reeds goed bestudeer is. Alkaantiol en di-alkiel disulfied is gebruik om SAMs te vorm. ‘n Verskeidenheid SAMs is vergelyk ten einde die anker te selekteer waaraan die hoogste konsentrasie lisosiem sal bind. Lisosiem is die effektiefste aan Au film lae ge-immobiliseer in die teenwoordigheid van SAM 3-merkapto-propanoësuur. Die swakste immobilisasie is in die teenwoordigheid van kombineerde SAM 11-merkapto-dekanoësuur/1-nanotiol waargeneem. Die sensitiwiteit van die ZnO nanodrade is in vitro getoets, in die teenwoordigheid van verskillende konsentrasies van lisosiem teenliggaampies. ‘n Toename in die dimensie van die ZnO grondlaag het die gemiddelde deursnit van die ZnO grein verhoog en so ook die gemiddelde deursnit van die gesintetiseerde ZnO nanodrade. Toediening van die ZnO grondlaag deur gebruik te maak van die RF silindriese mikrogolf-verstuiwings tegniek het die orientasie van die c-aslyn van die nanodrade verbeter. Toediening met die sol-gel draai-bedekkings tegniek het ‘n onreëlmatige orientasie van die c-aslyn teweeg gebring, asook ‘n variasie in die afmetings van die nanodrade. ‘n Toename in die Au laag het ‘n afname in die gemiddelde afmetings van die nanodrade en ook ‘n onreelmatige oriëntasie van die c-aslyn veroorsaak. In teenstelling met enkel-kristallyne Au (111) het poli-kristallyne Au lagies ‘n toename in die gemiddelde deursnit van die nanodrade veroorsaak. Die kristal-oriëntasie van die Au laag het geen effek op die belyning van die nanodrade gehad nie. Die spanningspotensiaal het verhoog met ‘n toename in teenliggaampie binding. Hiervolgens kan die ZnO nanosensor gebruik word om veranderinge in immunoglobulien vlakke te monitor. Teenliggaampie konsentrasies wat wissel van 10 ng/ml tot 20 μg/ml is opgespoor. Hierdie is die eerste studie wat toon dat ZnO nanodrade, omskep tot piëzo-elektriese transduseerders, gebruik kan word in die opsporing van teenliggaampies. Die grootte van die skyfie met die ZnO nanodrade is tans ongeveer 1 cm² en is te groot om in ‘n kompakte biosensor in te bou. Benewens die uitdaging om kleiner nanodraad skyfies te ontwikkel, sal hoogs sensitiewe sensors en seinversterkers ontwikkel moet word om die sein afkomstig van die nanodrade te versterk. Die biosensor sal ook ge-optimiseer moet word om ‘n verskeidenheid immunoglobuliene op te spoor.