Les travaux présentés dans ce manuscrit concernent la réalisation et la caractérisation d’un capteur de gaz à base de dispositifs à ondes élastiques de surfaces, SAW (Surface Acoustic Wave). Pour obtenir et exploiter de telles ondes, deux transducteurs inter-digités (IDT), l’un servant d’émetteur et l’autre de récepteur, sont déposés sur un substrat piézoélectrique. Une tension alternative appliquée aux bornes de l’IDT émetteur génère une onde se propageant le long du substrat. Lorsque cette onde arrive sur l’IDT récepteur, elle est convertie en tension électrique. A partir de ce dispositif, la spécificité du capteur est obtenue par l’ajout d’une couche sensible sur le chemin de propagation de l’onde, entre les deux IDTs. L’adsorption du gaz sur la couche sensible perturbe la propagation de l’onde et modifie ainsi sa vitesse et son amplitude. La structure du capteur développé et caractérisé au cours de cette thèse est la suivante : Polyaniline/ZnO/Quartz. Le substrat bicouche ZnO/Quartz pour une direction de propagation particulière (90°) constitue la partie génératrice d’ondes de Love et la polyaniline, polymère fonctionnalisable est utilisée en tant que couche sensible. La structure génératrice d’ondes a été entièrement réalisée en salle blanche avec notamment l’optimisation des paramètres de dépôt du film de ZnO par pulvérisation réactive RF magnétron et la photolithographie des IDTs. Elle a ensuite été étudiée et caractérisée, avant et après dépôt de la couche sensible, par des mesures expérimentales confrontées aux estimations théoriques. Pour finir, nous avons procédé à des tests sous gaz (NO2, SO2 et éthanol) avec notre capteur. Nous avons ainsi pu montrer le potentiel d’utilisation de la structure Polyaniline/ZnO/Quartz en tant que capteur de gaz. / The work presented in this book concerns the realization and characterization of a gas sensor based on surface acoustic wave (SAW) devices. To obtain and work with these waves, two interdigital transducers, one emitting and one receiving, are deposited on a piezoelectric substrate. An alternating input signal at the emitting IDT stimulates a wave that propagates along the substrate. At the receiving IDT, this wave is converted into electrical output signal. To obtain a gas sensor, a sensitive film is added in the path of the wave, between the IDTs. The gas adsorption on the sensitive film perturbs the wave propagation and modifies its velocity and amplitude. The sensor structure developed and characterized during this PhD thesis is the following : Polyaniline/ZnO/Quartz. The two layers ZnO/Quartz substrate, for a 90° propagating direction, generates the Love waves and the polyaniline, polymer that can be modified by functional groups is used as sensitive layer. The waves generating structure has been realized entirely in a clean room, especially with the optimisation of the ZnO films deposition by RF magnetron reactive pulverisation process and the photolithography of the IDTs. Then, this structure has been studied and characterized, before and after the sensitive layer deposition, with experimental measurements compared with theoretical estimations. Finally, we have made gas tests (NO2, SO2 and ethanol) with the sensor. In this way, we have shown that the Polyaniline/ZnO/Quartz structure can be used as gas sensor.

Little research has been done to determine the stress states developed in an industrial sawblade for various operating conditions. The stresses are developed from the forces generated during the cutting of materials, and also from the vibration of the sawblade. The difficulty of analyzing these stresses and vibrations results from the sawblade's high speed of rotation, which make it difficult to instrument the sawblade for analysis. Stress and vibration can ruin the sawblade from loss of material properties due to heat build-up and fatigue failure. The sawblade industry raised natural frequencies away from the operating frequencies to overcome the vibrations. To raise the natural frequencies of the sawblades away from the operating frequencies, residual stresses have been intentionally induced in the sawbody. The residual stresses come from plastically deforming the sawbody with one or more concentric rings. Experts who determine the location, depth, and number of residual stress rings are called "saw doctor". This thesis quantifies the residual stresses induced by saw doctors. Developing and evaluating finite element models of an industrial sawblade while undergoing the effects from rotating and cutting are also included in the thesis. In addition, the effects on the sawblades performance due to various numbers and lengths of expansion slots and sawblade tensioning are explored. Models of the sawblade are plastically deformed leaving residual stresses which are analyzed to determine the natural frequencies of the sawblade. The thesis quantifies the above mechanisms for a sawblade under the loads developed from rotation and a load case representing the cutting process. The work developed in this thesis is a first step toward characterizing the effects of specific mechanisms which can be used to design better, longer lasting sawblades. / Master of Science

Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 91-93).

La thèse traite des capteurs à ondes élastiques de surface (SAW) et plus particulièrement de leur application pour la mesure des basses pressions et des hautes températures. Le premier chapitre est consacré à l’histoire des dispositifs SAW, depuis 1965. Les principes de fonctionnement des capteurs SAW sont décrits, ainsi que leurs avantages concurrentiels. La seconde partie du document concerne les outils théoriques utilisés pour la modélisation des ondes élastiques et pour la prévision de leur sensibilité aux perturbations. Des formules pour le calcul de la sensibilité à la déformation ou à la variation de température sont démontrées. Les approches de Nalamwar/Epstein et Tiersten sont toutes deux présentées pour le calcul de l’effet des déformations. La troisième partie de la thèse est consacrée à l’étude théorique et expérimentale d’un nouveau concept de capteur SAW de pression (proposé par l’auteur), pour la mesure précise du vide primaire et secondaire. Les résultats expérimentaux confirment l’ensemble des prévisions théoriques. Cette innovation a été brevetée fin 2006. Un design « ultime » de type MEMS est proposé pour maximiser les performances du capteur. Enfin, la dernière partie du document traite des capteurs SAW « wireless » passifs comme une solution prometteuse pour la mesure des hautes températures. La problématique des matériaux est abordée, ainsi que celle du calcul du TCD pour des structures bicouche. L’effet du champ de déformations généré par la dilatation thermique différente des couches est pris en compte pour améliorer la précision du calcul théorique du TCD. Cette approche est étayée par des résultats théoriques et expérimentaux. / The thesis deals with the application of SAW sensors for low pressure and high temperature measurements. The first chapter is devoted to the history of SAW devices, from 1965. The principles of SAW sensors are described, as well as their industrial and economical potentials. The second part is devoted to the theoretical tools, used to model the basic properties of elastic waves as well as their sensitivity to external disturbances. Formulas for calculating the sensitivity of devices under strain or temperature changes are inferred. The approaches of Nalamwar/Epstein and Tiersten to take into account the effect of strain fields are both presented. The third part is devoted to the study of a new SAW pressure sensor concept (suggested by the author), for the accurate measurement of primary and secondary vacuum. The experimental results confirm the theoretically predicted sensor parameters: measuring range, sensitivity, precision and response time. A patent is pending for this innovation. A more efficient MEMS-type design is elaborated to maximize the level of performances. Finally, the thesis deals with wireless passive SAW sensor as a very promising solution for measurement at high temperature. The issue of materials is discussed, as well as the classical way to calculate the Temperature Coefficient of Delay (TCD) for multilayered structures. The effect of the strain field induced in the SAW structure by the differential thermal expansion of the different layers is taken into account to improve the accuracy of TCD calculations. This original theoretical approach is supported by experimental and theoretical results.

The highly c-axis oriented ZnO films were deposited on silicon substrates by reactive RF magnetron sputtering in this study. The optimal two-step deposition parameters for ZnO films, which are oxygen concentrations of 70 % (1st step) and 50 % (2nd step), RF power of 100 W and sputtering pressure of 25 mTorr, are obtained by means of XRD, SEM and AFM analysis. Al films are deposited under optimal deposition parameters, which are DC power of 100 W and sputtering pressure of 4 mTorr, to form IDT electrodes with low sheet resistances. Therefore, Al/ZnO/Si layered SAW devices were fabricated under these optimized manufacturing parameters. An oscillator based on a Al/ZnO/Si layered SAW device was fabricated for the application of UV detection and then investigating the acoustoelectric effect between surface acoustic wave and ultraviolet light illumination. Due to the fact that the sensor sensitivity is directly proportional to the resonance frequency, in this study the SAW device with high resonance frequency of Sezawa mode is adopted to form SAW oscillator for high sensitivity. The resonance frequency of SAW oscillator is 751.41 MHz. The optimal detecting zone for UV light is the center of IDT electrode with maximum sensitivity of 8.12 ppm/(£gW/cm2).

Photonic crystal (PtC) cavities are an increasingly important way to create all optical methods to control optical data. Not only must the data be controlled, but interfacing it with high frequency electrical signals is particularly interesting especially if this occurs in the 1.55µm telecom band. We present an experiment that uses Rayleigh surface acoustic waves (SAWs) to modulate the frequency of the guided mode of an L3-cavity PtC created on a silicon slab. This work has the potential to interface optical and electrical signals via a mechanical strain wave operating at gigahertz frequencies. Defects are carefully designed into a triangular lattice PtC to realize a waveguide coupled optical cavity. The cavity can be experimentally accessed through grating couplers excited by polarized light at 10 degrees incidence from normal. The optical components are fabricated on a silicon-on-insulator platform, with light confined to the silicon slab region. Through transmission experiments, the L3 cavity was found to have a narrow resonance characterized by a Lorentzian distribution. A quality factor of 165 centered at 6255 1/cm (1.599µm) was measured. Aluminum interdigitated transducers (IDTs) were fabricated through a lithography liftoff process. Their ability to create SAWs requires a piezoelectric medium. As silicon does not have this property, growth of a thin ZnO film was required. The transducers were measured using a network analyzer and were found to produce Rayleigh SAWs at a frequency of 179MHz and a wavelength of 24µm. The acoustic energy traveled 70µm to the target optical device. The L3 cavity has dimensions of around 4µm a side - less than 1/2 a SAW wavelength. Modulation of the L3 PtC resonant frequency was monitored through a repeat of the transmission experiment but with RF excitation of the IDTs at the SAW frequency. A broadening of the transmission spectrum was expected. Unfortunately no change in the fitting parameters could be measured. An HF etch was used to undercut the L3 PtC such that a silicon slab suspended in air could be realized. Simulations had been conducted showing an order of magnitude increase in the quality factor was possible. Broken wirebonds on the transducers created unintended etch channels rendering the SAW non-operational. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-04-29 12:33:49.254

Made available in DSpace on 2014-06-12T17:40:56Z (GMT). No. of bitstreams: 2 arquivo7089_1.pdf: 2259442 bytes, checksum: 4851aab70d2479c859a5ccbdc3d8260a (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2005 / O desenvolvimento atual em sensores tem como objetivo, uma maior integração entre o componente sensível e o circuito eletrônico para detecção, processamento e comunicação, de maneira que todos os componentes sejam fabricados no mesmo chip. Esse tipo de sensor é denominado genericamente de sensor inteligente integrado (integrated smart sensor). A sua simulação requer modelos que possam ser utilizados em simuladores de circuito. SPICE é um simulador de propósito geral e tem sua estrutura presente em vários outros simuladores comerciais. Ele foi projetado desde o início para ser uma ferramenta de simulação de circuitos integrados. Dispositivos a Onda Acústica de Superfície, OAS (em inglês, SAW = "Surface Acoustic Wave") têm diversas aplicações devido as suas várias vantagens, tais como: baixo custo, leveza, reduzido tamanho e operação passiva. Modelos de tansdutores acústicos têm sido propostos, mas apenas um deles pode ser utilizado em algumas versões do SPICE (PSPICE e HSPICE). Todos apresentam complexidade ao representar transdutores longos. Nosso modelo é baseado em m modelo obtido a partir das equações dos modos acomplados, é compacto e tem sido utilizado, com sucesso, em diversas versões do SPICE, desde o SPICE 3f4, disponível gratuitamente até o ELDO da Mentor Graphics Corp

In this thesis a model is developed to characterise the behaviour of layered SAW 2- port resonator sensors operating in liquid media. In the critical review of literature, it is found that methods based on the periodic Green's function combined with the COM model are best suited to this task. However, an important deficiency of this approach is the lack of a good model for electrodes buried within layered media. This deficiency is resolved in this thesis by the formulation of a periodic matrix eigen-operator, using a phase-shifted Fourier series representation. This model is then utilised in the study of resonator behaviour as a function of guiding layer thickness, including the mass sensitivity. Based on this modelling work, a SAW resonator structure is designed, and its frequency response is found to be in generally good agreement with theoretical predictions. The mass sensitivity of this device is then analysed using both theoretical and experimental means. In contrast to the sensitivity analyses found in the literature, sensitivity variation across the device surface is considered in this work. For the resonator structure it is found that sensitivity is greatest at the device centre, with the ends of the device making negligible contribution to the complete device response. The result is that the sensitive material may be deposited only in a small region in the centre of the device, with minimal reduction in device response.

Currently, the demand for natural gas is increasing as a result of high world energy consumption and rising environmental awareness. As the exploration of natural gas field is expanding towards remote regions, long distance pipelines have been developed. The economical, environmental, and safe movement of gas to the marketplace requires that transmission pipelines designed to operate at high pressure should possess adequate strength and improved toughness over a variety of temperature ranges. The purpose of this research was to investigate the effect of submerged arc welding (SAW) parameters on the quality and mechanical properties of X80 steel, which was supplied by IPSCO Inc., Regina. The welding was performed using single and double wires and different speeds (16.93, 19.69, 25.4, 29.63 and 33.87mm/s). The weld quality was evaluated using non-destructive testing methods (NDT) such as visual inspection, radiography, and ultrasonic test. The weld bead characteristics were studied using weld geometry measurements. The relationship between the microstructures and mechanical properties of weld deposits was studied by means of hardness measurements, Charpy V-notch test, lateral expansion measurements, tensile test, optical metallography, image analysis, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS).<p>It was found that there was a limit to which welding speed could be increased without the weld suffering from severe defects such as lack of penetration and undercut. The use of more than one welding wire improved the maximum welding speed at which good weld quality was maintained. Increasing the welding speed resulted in changes in the weld microstructure through the formation of higher percentage of fine acicular ferrite (AF) grain structure and a reduction in the amount of grain boundary ferrite (GBF) in the weld metal. Changing weld speed also reduced the size of the heat affected zone (HAZ). All of this resulted in improved the mechanical properties of the welded joints.

Currently, the demand for natural gas is increasing as a result of high world energy consumption and rising environmental awareness. As the exploration of natural gas field is expanding towards remote regions, long distance pipelines have been developed. The economical, environmental, and safe movement of gas to the marketplace requires that transmission pipelines designed to operate at high pressure should possess adequate strength and improved toughness over a variety of temperature ranges. The purpose of this research was to investigate the effect of submerged arc welding (SAW) parameters on the quality and mechanical properties of X80 steel, which was supplied by IPSCO Inc., Regina. The welding was performed using single and double wires and different speeds (16.93, 19.69, 25.4, 29.63 and 33.87mm/s). The weld quality was evaluated using non-destructive testing methods (NDT) such as visual inspection, radiography, and ultrasonic test. The weld bead characteristics were studied using weld geometry measurements. The relationship between the microstructures and mechanical properties of weld deposits was studied by means of hardness measurements, Charpy V-notch test, lateral expansion measurements, tensile test, optical metallography, image analysis, scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS).<p>It was found that there was a limit to which welding speed could be increased without the weld suffering from severe defects such as lack of penetration and undercut. The use of more than one welding wire improved the maximum welding speed at which good weld quality was maintained. Increasing the welding speed resulted in changes in the weld microstructure through the formation of higher percentage of fine acicular ferrite (AF) grain structure and a reduction in the amount of grain boundary ferrite (GBF) in the weld metal. Changing weld speed also reduced the size of the heat affected zone (HAZ). All of this resulted in improved the mechanical properties of the welded joints.