Les dépôts de YSZ, élaborés par projection plasma, sont des céramiques réfractaires généralement utilisées pour les applications de barrières thermiques (TBC). Sa faible conductivité thermique associée à sa bonne résistance mécanique assure aux TBC de hautes performances et de bons rendements. La structure et la microstructure complexe sont à l'origine de ces propriétés mécaniques, et celles doivent être contrôlées. Tout comme les céramiques denses la YSZ se dégrade en température et sous vapeur d'eau.La dégradation des propriétés mécaniques dans le temps (module d'élasticité et contrainte à rupture)est accélérée par la température. Pour cette étude les propriétés ont été évaluées en flexion 3 points à température ambiante. Les observations structurales et microstructurales ont été réalisées respectivement par DRX et microscopie électronique à balayage au cours du vieillissement. Un model analytique a pu être proposé pour prédire le comportement du matériau dans le temps sous humidité. / Yttria Stabilized Zirconia (YSZ) coatings, deposited by plasma sprayed process, are refractory ceramics mostly used as the Thermal Barrier Coating (TBC) applications. The low YSZ thermal conductivity associated to the good mechanical resistance ensures a high performances and efficiencies of these TBC. The structure and the complex microstructure are responsible for the mechanical properties and must be controlled. Like brittle ceramic materials, the YSZ is affected by degradation at low temperature due to water vapor. Material ageing results from the progressive degradation of the mechanical properties (such as fracture strength and Young’s modulus), which seem to decrease in time and accelerate depending on temperature. In this study, the mechanical properties have been evaluated by means of three-point bending tests at room temperature. The observations of the structure and the microstructure are respectively investigated by X-ray diffraction and SEM-technique with material ageing. An analytical model is suggested in order to predict the evolution of the properties under humidity atmosphere.

Dans le domaine de la santé, l’analyse de l'haleine expirée offre un outil simple et non invasif pour le diagnostic précoce des maladies. Les capteurs de gaz à base de SnO2 modifies semblent être des dispositifs prometteurs pour détecter les gaz polaires tels que l'ammoniac. Dans cette étude, la fonctionnalisation de la surface de SnO2 a été réalisée afin d'obtenir un capteur de gaz sensible et sélectif à l'ammoniac, qui fonctionne à température ambiante. La première étape de la fonctionnalisation est la fixation covalente d’un film de 3-aminopropyltrethoxysalane (APTES) sur SnO2 en phase vapeur ou liquide. Les caractérisations effectuées par Spectroscopie Infrarouge et Spectrométrie photoélectronique X montrent qu’une quantité plus importante d'APTES a été greffée en phase liquide hydratée. La deuxième étape consiste à fonctionnaliser le SnO2-APTES avec des molécules contenant du chlorure d'acyle avec différents groupes tel que des groupes alkyle, acide et ester. Les capteurs modifiés par des acides et des esters sont sensibles à l’ammoniac entre 0,2 et 10 ppm à température ambiante. Cependant, le SnO2 APTES modifié par l’ester s'est révélé être plus sélectif que le capteur modifié par l'acide pour l’ethanol et le mondxyde de carbone. Ces résultats impliquent que la réponse est générée par les groupes fonctionnels acide et ester, NH3 modifie le moment dipolaire de la couche moléculaire greffée, ce qui entraine une modification de la conductance de SnO2. Le fonctionnement à température ambiante est l'un des avantages de ces capteurs, tout comme leur sélectivité à l'ammoniac en regard d'autres gaz tels que l'éthanol, le monoxyde de carbone et l'acétone. / One of the major challenges in the modern era is how we can detect the disease when we are still feeling healthy via noninvasive methods. Exhaled breath analysis is offering a simple and noninvasive tool for early diagnosis of diseases. Molecularly modified SnO2 sensors seem to be promising devices for sensing polar gases such as ammonia. SnO2 surface functionalization was performed in order to obtain sensitive and selective ammonia gas sensor that operates at room temperature. The first step of functionalization is the covalently attachment of 3-aminopropyltriethoxysilane (APTES) film on SnO2 in vapor or liquid phases. The characterization performed by the Infrared Spectroscopy and X-ray Photoelectron Spectroscopy, show that more APTES were grafted by hydrous liquid phase silanization. The second step was the functionalization of APTES modified SnO2 with molecules having acyl chloride of end functional groups molecules such as alkyl, acid and ester groups. Pure SnO2 and APTES modified SnO2 sensors did not show any significant sensitivity to ammonia (0.2-100 ppm) at 25 °C. On the contrary, acid and ester modified sensors are sensitive to ammonia between 0.2 and 10 ppm at room temperature. However, ester modified SnO2 was more selective than acid modified sensor regarding the ethanol and carbon monoxide gases. Ammonia variates the attached molecular layer’s dipole moment which leads to change in SnO2 conductance. Working at ambient temperature is also one of the advantages of these sensors in addition to the selectivity to ammonia regarding other gases such as ethanol, carbon monoxide and acetone.

Este trabalho tem como objetivo avaliar o desempenho metrológico de 15 unidades eletrocirúrgicas de dois fabricantes e três modelos diferentes quando submetidos a variações de temperatura ambiente. Para tanto foram considerados cinco níveis do fator temperatura e três pontos da faixa nominal das potências de corte e de coagulação. Os ensaios foram realizados acoplando a unidade eletrocirúrgica objeto de avaliação a um analisador de potência. O teste de Tukey foi aplicado visando efetuar múltiplas comparações entre os níveis do fator temperatura. Os parâmetros metrológicos incerteza de medição, erro, repetibilidade e erro máximo foram estimados para todos as unidades avaliadas. A incerteza associada à medição foi avaliada de acordo com as recomendações do Guia para a Expressão da Incerteza de Medição (GUM). A análise de variância (ANOVA), o teste de Tukey e o boxplot indicaram efeitos estatisticamente significativos do fator temperatura nos valores de potência de corte e coagulação avaliados. A incerteza expandida associada aos valores de potência de corte e de coagulação aumentou de forma significativa na medida em que estas se aproximaram do limite superior da faixa nominal. Foram observadas diferenças significativas entre as unidades eletrocirúrgicas dos fabricantes A e B sobre tudo para menores valores de potência. Neste sentido as unidades do fabricante A apresentaram desempenho superior. Nas potências de corte 50 W, 150 W e 300 W, observou-se que 33 %, 87 % e 100 %, respectivamente, das unidades avaliadas apresentaram valores de erro máximo maiores que 5 W e portanto não atendem ao critério especificado pelo fabricante. Para as potências de coagulação, 30 W, 80 W e 120 W estas porcentagens foram respectivamente de 0, 53 % e 60 %. As unidades eletrocirúrgicas avaliadas apresentam um desempenho que podem comprometer o sucesso do processo cirúrgico. / The objective of this work is to evaluate the metrological performance of 15 electrosurgical unit from two manufacturers and three different models when subjected to ambient temperature variations. For this, five levels of the temperature factor and three points of the nominal range of the cutting and coagulation powers were considered. The tests were performed by coupling the evaluation electrosurgical unit to a power analyzer. The Tukey test was applied in order to make multiple comparisons between the levels of the temperature factor. The metrological parameters measurement uncertainty, error, repeatability and maximum error were estimated for all evaluated electrosurgical unit. The uncertainty associated with the measurement was evaluated according to the recommendations of the Guide to the Expression of Uncertainty in Measurement (GUM). Analysis of variance (ANOVA), Tukey test and boxplot indicated significant statistically effects of the temperature factor on the cutting and coagulation power values. The expanded uncertainty associated with cutting and coagulation power values increased significantly as they approached the upper limit of the nominal range. Significant differences were observed between the scalpels of manufacturers A and B mainly for lower power values. The scalpels of the manufacturer A presented superior performance. At 50 W, 150 W and 300 W cutting powers, it was observed that 33 %, 87 % and 100 %, respectively, of the scalpels had maximum error values greater than 5 W and therefore they did not meet the criterion specified by the manufacturer (maximum error must be less than 5 W). For the coagulation powers, 30 W, 80 W and 120 W these percentages were respectively 0, 53 % and 60 %. The electrosurgical unit evaluated have a metrological performance that can compromise the success of the surgical process. / Dissertação (Mestrado)

L’objectif de cette thèse est de développer un matériau à base de polyméthacrylate de méthyle (PMMA) amorcé par une réaction redox à température ambiante pour produire des composites thermoplastiques. Plus particulièrement, notre travail a consisté à étudier le mécanisme d’amorçage afin d’améliorer la formulation de la résine en terme de cinétique de polymérisation. Afin d’atteindre cet objectif, les paramètres d’Arrhenius de la décomposition d’amorceur ont été déterminés et intégrés dans un modèle de simulation numérique décrivant la polymérisation du MMA à température ambiante développé à l’aide du logiciel PREDICI. Basé sur cette simulation, des différents paramètres ont été testés dans le but de diminuer le temps de polymérisation. En complément de la détermination des paramètres du système d’amorçage, une étude de copolymérisation avec un grand nombre de comonomères a été effectuée. Cette étude a conduit à l’identification d’un monomère permettant d’accélérer la vitesse de polymérisation : le méthacrylate d’acetoacetoxyethyle (AAEMA). Une étude cinétique de ce monomère a été réalisée avec l’identification du coefficient de la vitesse de propagation kp ainsi que les paramètres de copolymérisation avec MMA, rMMA et rAAEMA. Les paramètres cinétiques, qui ont été déterminés expérimentalement, ont été vérifiés par une simulation numérique de copolymérisation de MMA et AAEMA. / Composite materials are used for decades as high-performance materials in industry. Up to date these materials were based on non-recyclable thermoset polymers. Nowadays, environmental and economical restrictions enhance the development of recyclable composite materials. For answering that demand, research focuses on the development of recyclable thermoplastic polymer composites. Within this context, the work of this thesis focuses on the development of a material based on a poly(methyl methacrylate) (PMMA) resin initiated with a redox initiation system at room temperature in order to prepare thermoplastic composites. More precisely, our work consisted of studying this initiation system and to improve the kinetics of the resin formulation. For that purpose, the Arrhenius parameters of the initiator decomposition reaction were determined and implemented in a simulation model that describes the polymerization of MMA at room temperature. Based on the simulation carried out on the software PREDICI, several conditions were tested aiming in the decrease of the polymerization times. Besides investigating parameters concerning the initiation system, a copolymerization study, using a large variety of comonomers, was conducted. This study led to the identification of an interesting fast polymerizing methacrylate: acetoacetoxyethyl methacrylate (AAEMA). The kinetics of this monomer were studied including the determination of the propagation rate coefficient kp and the copolymerization parameters with MMA rMMA and rAAEMA. The determined kinetic parameters were finally verified by a copolymerization simulation of MMA and AAEMA.

No description available.

The deposition of boron oxide (B₂O₃) films on silicon substrates is of significant interest in microelectronics for ultrashallow doping applications. However, thickness control and conformality of such films has been an issue in high aspect ratio 3D structures which have long replaced traditional planar transistor architectures. B₂O₃ films are also unstable in atmosphere, requiring a suitable capping barrier for passivation. The growth of continuous, stoichiometric B₂O₃ and boron nitride (BN) films has been demonstrated in this dissertation using Atomic Layer Deposition (ALD) and enhanced ALD methods for doping and capping applications. Low temperature ALD of B₂O₃ was achieved using BCl₃/H₂O precursors at 300 K. In situ x-ray photoelectron spectroscopy (XPS) was used to assess the purity and stoichiometry of deposited films with a high reported growth rate of ~2.5 Å/cycle. Free-radical assisted ALD of B₂O₃ was also demonstrated using non-corrosive trimethyl borate (TMB) precursor, in conjunction with mixed O₂/O-radical effluent, at 300 K. The influence of O₂/O flux on TMB-saturated Si surface was investigated using in situ XPS, residual gas analysis mass spectrometer (RGA-MS) and ab initio molecular dynamics simulations (AIMD). Both low and high flux regimes were studied in order to understand the trade-off between ligand removal and B₂O₃ growth rate. Optimization of precursor flux was discovered to be imperative in plasma and radical-assisted ALD processes. BN was investigated as a novel capping barrier for B₂O₃ and B-Si-oxide films. A BN capping layer, deposited using BCl₃/NH₃ ALD at 600 K, demonstrated excellent stoichiometry and consistent growth rate (1.4 Å/cycle) on both films. Approximately 13 Å of BN was sufficient to protect ~13 Å of B₂O₃ and ~5 Å of B-Si-oxide from atmospheric moisture and prevent volatile boric acid formation. BN/B₂O₃/Si heterostructures are also stable at high temperatures (>1000 K) commonly used for dopant drive-in and activation. BN shows great promise in preventing upward boron diffusion which causes a loss in the dopant dose concentration in Si. The capping effects of BN were extended to electrochemical battery applications. ALD of BN was achieved on solid Li-garnet electrolytes using halide-free tris(dimethylamino)borane precursor, in conjunction with NH₃ at 723 K. Approximately 3 nm of BN cap successfully inhibited Li₂CO₃ formation, which is detrimental to Li-based electrolytes. BN capped Li-garnets demonstrated ambient stability for at least 2 months of storage in air as determined by XPS. BN also played a crucial role in stabilizing Li anode/electrolyte interface, which drastically reduced interfacial resistance to 18 Ω.cm², improved critical current density and demonstrated excellent capacitance retention of 98% over 100 cycles. This work established that ALD is key to achieving conformal growth of BN as a requirement for Li dendrite suppression, which in turn influences battery life and performance.

In general, server rooms have restricted access requiring that staff possess access codes, keys, etc. Normally, only administrators are provided access to protect the physical hardware and the data stored in the servers. Servers also have firewalls to restrict outsiders from accessing them via the Internet. Servers also cost a lot of money. For this reason, server rooms also need to be protected against overheating. This will prolong the lifecycle of the units and can prevent data loss from hardware failure. The California State University San Bernardino (CSUSB), Specifically the College of Arts and Letters server room has faced power failures that affected the Air Conditioning Unit (AC) and as a result the room became overheated for a long time, causing hardware failure to server units. This is why this project is important for the College and needs to be implemented as soon as possible. The administrator’s old method of controlling server room temperature was by manually adjusting the temperature box inside of the server room. Now it can be controlled and monitored using remote access. The purpose of A Web-Based Temperature Monitoring System for the College of Arts and Letters proposed in this project is to allow users to monitor the server room temperature through a website by using any computer or mobile device that has Internet access. Also, this system notifies users when the room attains a critical temperature by sending an email/text to the server room administrator. A Web-Based Temperature Monitoring System for the College of Arts and Letters project is for the exclusive use of the College of Arts & Letters (CAL) server room. The administrator is the only person that can grant access to others by creating a proper account. For this project three prototypes will be implemented, first to measure the current server room temperature, the second to show the temperature history of the room, and third to use the built-in search system to locate times that given temperatures were attained.

No description available.

Die vorliegende Arbeit beschreibt einen neuartigen Fügeprozess, das sogenannte reaktive Fügen bzw. Bonden. Hierbei werden sich selbsterhaltene exotherme Reaktionen in nanoskaligen Schichtsystemen als lokale Wärmequelle für das Fügen unterschiedlichster Substrate der Mikrosystemtechnik verwendet. Das Bonden mit den reaktiven Systemen unterscheidet sich von herkömmlichen Verfahren der Aufbau- und Verbindungstechnik primär dadurch, dass durch die rasche Reaktionsausbreitung bei gleichzeitig kleinem Reaktionsvolumen die Fügetemperaturen unmittelbar auf die Fügefläche beschränkt bleiben. Entgegen den herkömmlichen Fügeverfahren mit Wärmeeintrag im Volumen, schont das neue Verfahren empfindliche Bauteile und Materialien mit unterschiedlichsten thermischen Ausdehnungskoeffizienten lassen sich besser verbinden. In der vorliegenden Arbeit werden die Grundlagen zur Dimensionierung, Prozessierung und Integration der gesputterten reaktiven Materialsysteme beschrieben. Diese Systeme werden verwendet, um heterogene Materialien mit unterschiedlichen Durchmessern innerhalb kürzester Zeit auf Wafer-Ebene und bei Raumtemperatur zu bonden. Die so erzeugten Verbindungen werden hinsichtlich der Mikrostruktur, der Zuverlässigkeit sowie der Dichtheit untersucht und bewertet. Zusätzlich wird die Temperaturverteilung in der Fügezone während des Fügeprozesses mit numerischen Methoden vorhergesagt.

Recently, we have described the synthesis of chiral metal–organic frameworks iPr-ChirUMCM-1 and Bn-ChirUMCM-1 and their use in enantioselective separation. Here, we demonstrate for the first time the use of a chiral solvating agent (1-phenyl-2,2,2-trifluoroethanol, TFPE) for chiral recognition in iPr-ChirUMCM-1 and Bn-ChirUMCM-1 by means of solid-state13C NMR spectroscopy. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.