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Electrical Resistivity Imaging of Preferenital Flow through Surface Coal Mine Valley Fills with Comparison to Other Land FormsGreer, Breeyn 20 April 2015 (has links)
Surface coal mining has caused significant land-use change in central Appalachia in the past few decades. This landscape altering process has been shown to degrade water quality and impact aquatic communities in the mining-influenced headwater streams of this biodiverse ecoregion. Among pollutants of concern is total dissolved solids (TDS) which is usually measured via its surrogate parameter, specific conductance (SC). The SC of valley fill effluent is a function of fill construction methods, materials, and age; yet hydrologic studies that relate these variables to water quality are sparse due to the difficulty of implementing traditional hydrologic measurements in fill material. We tested the effectiveness of electrical resistivity imaging (ERI) to monitor subsurface hydrologic flow paths in valley fills. ERI is a non-invasive geophysical inverse technique that maps spatiotemporal changes in resistivity of the subsurface. When a resistance or conductive change is induced in the system, ERI can reveal both geologic structure and hydrologic flows. We paired ERI with artificial rainfall experiments to track highly conductive infiltrated water as it moved through the valley fill. The subsurface structure of two other landforms were also imaged to confirm variations between forms. Results indicate that ERI can be used to identify the subsurface geologic structure as well as track the advancing wetting front and preferential flow paths. We observed that the upper portion of a fill develops a profile that more closely resembles soil with smaller particle sizes, while the deeper profile has higher heterogeneity, with large rocks and void spaces. The sprinkling experiments revealed that water tends to pond on the surface of compacted areas until it reaches preferential flowpaths, where it infiltrates quickly and migrates deeply or laterally. We observed water moving from the surface down to a 20 meters depth in one hour and 15 minutes, and to a depth of 10 meters in just 45 minutes. We also observed lateral preferential flow downslope within 5 meters of the surface, likely due to transmissive zones between compacted layers along the angle-of-repose. Finally, when compared to other landscapes we were able to see that a filled highwall slope has larger rocks near the surface than the valley fill, but a similar degree of heterogeneity throughout; while the natural slope has less heterogeneity at depth as is expected in consolidated bedrock. ERI applications can improve understanding of how various fill construction techniques influence subsurface water movement, and in turn aid in the development of valley fill construction methods that will reduce environmental impacts. / Master of Science
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Monitoring damage of concrete beams via self-sensing cement mortar coating with carbon nanotube-nano carbon black composite fillersQiu, L., Li, L., Ashour, Ashraf, Ding, S., Han, B. 26 July 2024 (has links)
Yes / Self-sensing concrete used in coating form for structural health monitoring of concrete structures has the merits of cost-effectiveness, offering protective effect on structural components, enabling electrical measurements unaffected by steel reinforcement and is also convenient to maintain and replace. This paper investigates the feasibility of using self-sensing cement mortar coating containing carbon nanotube-nano carbon black (CNT-NCB) composite fillers (CNCFs) for damage monitoring of concrete beams. The self-sensing cement mortar coated to concrete beams demonstrated outstanding electrical conductivity (resistivity ranging from 18 to 85 Ω·cm). Under monotonic flexural loadings, self-sensing cement mortar coating with 1.8 vol.% CNCFs featured sensitive self-sensing performance in terms of capturing the initiation of vertical cracks at pure bending span of concrete beams, with fractional change in resistivity (FCR) reaching up to 60.6%. Moreover, FCR variations of self-sensing cement mortar coating exhibited good synchronization and stability with the variation of mid-span deflections of concrete beams during cyclic flexural loadings irrespective of the contents of CNCFs and cyclic amplitudes. Remarkably, it was found that FCR of cement mortar coating basically showed a progressive upward tendency, representing irreversible increase in the resistance during cyclic loading. The irreversible residual FCR indicated the crack occurrence and damage accumulation of concrete beams. / National Science Foundation of China (52368031, 51978127 and 52178188) and the China Postdoctoral Science Foundation (2022M710973)
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System Design, Fabrication, and Characterization of Thermoelectric and Thermal Interface Materials for Thermoelectric DevicesWang, Jue 13 June 2018 (has links)
Thermoelectric devices are useful for a variety of applications due to their ability to either convert heat directly into electricity, or to generate a temperature gradient from an electric current. These devices offer several attractive features including compact size, no moving parts, limited maintenance requirements, and high reliability. Thus thermoelectric devices are used for temperature-control, cooling, or power generation in various industrial systems such as automobiles, avionics, refrigerators, chillers, laser diodes, dehumidifiers, and a variety of sensors. In order to improve the efficiency of thermoelectric devices, many endeavors have been made to design and fabricate materials with a higher dimensionless thermoelectric figure of merit (ZT), as well as to optimize the device structure and packaging to manage heat more effectively. When evaluating candidate thermoelectric materials, one must accurately characterize the electrical conductivity, thermal conductivity, and the Seebeck coefficient over the temperature range of potential use. However, despite considerable research on thermoelectric materials for decades, there is still significant scatter and disagreement in the literature regarding accurate characterization of these properties due to inherent difficulties in the measurements such as requirements for precise control of temperature, simultaneous evaluation of voltage and temperature, etc. Thus, a well-designed and well-calibrated thermoelectric measurement system that can meet the requirements needed for multiple kinds of thermoelectric materials is an essential tool for the development of advanced thermoelectric devices.
In this dissertation, I discuss the design, fabrication, and validation of a measurement system that can rapidly and accurately evaluate the Seebeck coefficient and electrical resistivity of thermoelectric materials of various shapes and sizes from room temperature up to 600 K. The methodology for the Seebeck coefficient and electrical resistivity measurements is examined along with the optimization and application of both in the measurement system. The calibration process is completed by a standard thermoelectric material and several other materials, which demonstrates the accuracy and reliability of the system.
While a great deal of prior research has focused on low temperature thermoelectric materials for cooling, such as Bi2Te3, high temperature thermoelectric materials are receiving increasing attention for power generation. With the addition of commercial systems for the Seebeck coefficient, electrical resistivity, and thermal conductivity measurements to expand the temperature range for evaluation, a wide range of materials can be studied and characterized. Chapter Two of this dissertation describes the physical properties characterization of a variety of thermoelectric materials, including room temperature materials such as Bi0.5Sb1.5Te3, medium temperature level materials such as skutterudites, and materials for high temperature applications such as half-Heusler alloys. In addition, I discuss the characterization of unique oxide thermoelectric materials, which are Al doped ZnO and Ca-Co-O systems for high temperature applications.
Chapter Four of this dissertation addresses the use of GaSn alloys as a thermal interface material (TIM), to improve thermal transport between thermoelectric devices and heat sinks for power generation applications at high temperature. I discuss the mechanical and thermal behavior of GaSn as an interface material between electrically insulating AlN and Inconel heat exchangers at temperatures up to 600 °C. Additionally, a theoretical model for the experimental thermal performances of the GaSn interface layer is also examined. / Ph. D. / Thermoelectric materials can directly convert heat into electricity for power generation, or they can be used for cooling or refrigeration applications when supplied with electric power. This dissertation primarily focuses on the evaluation of materials used in thermoelectric generators (TEGs). Specifically, Chapter Two of this work describes the design, development, and validation of a developed measurement system that can evaluate two important properties, the Seebeck coefficient and electrical resistivity, for a variety of thermoelectric materials. Next, Chapter Three discusses the work using other commercial measurement systems to evaluate several types of thermoelectric materials, including Bi2Te3 based materials, skutterudites, half-Heusler alloys, ZnO, and Ca-Co-O for a TEG module. Finally, I discuss the use of GaSn, a liquid metal alloy, as a thermal interface material to improve heat transport between dissimilar materials for TEGs. The GaSn was applied between a thermoelectric device and a heat exchanger for use in energy harvesting devices. The mechanical robustness and thermal reliability were tested, and the GaSn was shown to improve thermal performances both in experiments and through modeling.
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Using Electrical Resistivity Imaging to Relate Surface Coal Mining Valley Fill Characteristics to Effluent Stream QualityLittle, Kathryn Leigh 04 April 2018 (has links)
Surface coal mining has altered Appalachian landscapes, affecting water quality and aquatic ecology. Valley fills created from excess overburden are prominent features of many mined landscapes. Increased total dissolved solids (TDS), as measured by its surrogate specific conductance (SC), is a significant water quality concern related to the exposure of fresh mineral surfaces to weathering in valley fills. Specific conductance levels in waters draining Appalachian mined areas are highly variable, yet the causes for this variability are not well known. Here we sought to improve understanding of such variability by investigating the interior subsurface structure and hydrologic flowpaths within a series of valley fills and relating that to valley fill characteristics such as age and construction method. We used electrical resistivity imaging (ERI) to investigate the subsurface structure of four valley fills in two dimensions. We combined ERI with artificial rainfall to investigate the location and transit time of hydrologic preferential infiltration flowpaths through the fills. Finally, we used our ERI results in conjunction with SC data from effluent streams to improve understanding of SC relationship to fill flowpaths and characteristics. ERI results indicated considerable variability in substrate type and widespread presence of preferential infiltration flowpaths among the valley fills studied. We estimated an average preferential flowpath length of 6.6 meters, average transit time of 1.4 hours, and average velocity of 5.1 m/h or 0.14 cm/s through preferential infiltration flowpaths. ERI successfully distinguished fills constructed using methods of conventional loose-dump and experimental controlled-material compacted-lift construction. Conventional fills had greater ranges of subsurface resistivity, indicating a wider range of substrate types and/or more variable moisture content. Conventional fills also showed more accumulation of water within the fill during artificial rainfall, possibly indicating more quick/deep preferential infiltration flowpaths than in the experimental fill. Relationships between other fill characteristics as well as stream effluent SC were not related in a statistically significant way to fill structure or flowpaths. ERI appears to be a robust non-invasive technique that provides reliable information on valley fill structure and hydrology, and experimental compacted-lift valley fill construction produces significantly altered hydrologic response, which in turn affects downstream SC. / MS / Surface coal mining has altered Appalachian landscapes, affecting water quality and aquatic ecology. Valley fills created from excess mine spoil are prominent features of many mined landscapes. The streams draining valley fills often have very poor water quality, including high levels of increased total dissolved solids (TDS) related to weathering of mine spoils within valley fills. In this work, we investigated the subsurface structure of a series of valley fills and identified preferential hydrologic flowpaths, which are the “paths of least resistance” water follows for rapid infiltration. We related our results to various valley fill characteristics such as age and construction method. We found that the subsurface of a conventionally built fill tends to have more variation in material and/or moisture content than a fill built with an experimental construction method. Conventional fills also showed more accumulation of water within the fill during artificial rainfall experiments, possibly indicating more quick/deep preferential infiltration flowpaths than in the experimental fill.
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Evaluating Preferential Recharge in Blue Ridge Aquifer Systems Using Saline TracersRugh, David F. 29 December 2006 (has links)
Multiple saline tracers were used to explore the role of geologic structure on groundwater recharge at the Fractured Rock Research Site in Floyd County, Virginia. Tracer migration was monitored through soil, saprolite, and fractured crystalline bedrock for a period of 3 months with chemical, physical, and geophysical techniques. Potassium chloride (KCl) and potassium bromide (KBr) tracers were applied at specific locations on the ground surface to directly test flow pathways in a shallow saprolite and deep fractured rock aquifer.
Previous work at the Fractured Rock Research Site have identified an ancient thrust fault complex that is present in the otherwise competent metamorphic bedrock; fracturing along this fault plane has resulted in a highly transmissive aquifer that receives recharge along the vertically oriented portion of the fault zone. A shallow aquifer has been located above the thrust fault aquifer in a heterogeneous saprolite layer that rapidly transmits precipitation to a downgradient spring.
Tracer monitoring was accomplished with differential electrical resistivity, chemical sampling, and physical monitoring of water levels and spring discharge. Tracer concentrations were monitored quantitatively with ion chromatography and qualitatively with differential resistivity surveys. KCl, applied at a concentration of 10,000 mg/L, traveled 160 meters downgradient through the thrust fault aquifer to a spring outlet in 24 days. KBr, applied at a concentration of 5,000 mg/L, traveled 90m downgradient through the saprolite aquifer in 19 days. KCl and KBr were present at the sampled springheads for 30 days and 33 days, respectively. Tracer breakthrough curves indicate diffuse flow through the saprolite aquifer and fracture flow through the crystalline thrust fault aquifer. Heterogeneities in the saprolite aquifer had a large effect on tracer transport, with breakthrough peaks varying several days over vertical distances of several meters.
Monitoring saline tracer migration through soil, saprolite, and fractured rock provided data on groundwater recharge that would not have been available using other traditional hydrologic methods. Travel times and flowpaths observed during this study support preferential groundwater recharge controlled by geologic structure. Geologic structure, which is not currently considered an important factor in current models of Blue Ridge hydrogeology, should be evaluated on a local or regional scale for any water resources investigation, wellhead protection plan, or groundwater remediation project. / Master of Science
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Caractérisation des discontinuités dans des ouvrages massifs en béton par la diagraphie électrique de résistivitéTaillet, Elodie January 2014 (has links)
Résumé : Le vieillissement des ouvrages en béton est une préoccupation majeure affectant la pérennité et l’efficacité des structures. Le maître d’ouvrage se doit de maintenir les fonctions d’usage de la structure tout en gardant une gestion économique efficace. L’objectif final de ces travaux de recherche est, donc de pouvoir renseigner sur l’état global de fissuration de la structure afin d’aider le maître d’ouvrage à respecter ses engagements.
Dans cette optique, cette thèse développe une nouvelle technique aidant à la quantification de l’état des ouvrages massifs en béton. Elle s’appuie, pour cela, sur la méthode non-destructive de résistivité électrique en surface, connue pour sa sensibilité face à des facteurs révélateurs d’une altération. Toutefois, à cause de sa dépendance entre la profondeur d’investigation et la résolution, la méthode ne peut pas garantir de l’état global d’un ouvrage. De ce fait, il a été décidé d’utiliser la résistivité électrique via des forages préexistants dans la structure (diagraphie électrique). L’outil utilisé est une sonde en dispositif normal réservée jusqu’à présent pour la prospection pétrolière et hydrogéologique. En plus d’une prospection en profondeur via le forage, cette sonde peut acquérir des informations sur un rayon de 3.2m autour du forage. Cependant, à mesure que le volume de béton sondé augmente, la résolution décroit. La difficulté est donc de pouvoir exploiter les capacités de prospection de la sonde tout en sachant que la résolution faillit. Il s’agit de contourner le problème en maîtrisant les concepts de la diagraphie et son nouveau milieu d’application.
Cette thèse est basée sur une première approche numérique permettant d’apporter des corrections sur les données de terrain et de déterminer la sensibilité de l’outil face à de l’endommagement d’ouverture plurimillimétrique à centimétrique. Ceci est validé par des mesures réalisées sur une écluse de la Voie Maritime du Saint-Laurent. Une étude numérique de la réponse de l’outil en fonction des paramètres de fissure tels que l’ouverture, le contraste entre la résistivité de la discontinuité et du béton, et l’extension est réalisée. Elle permet de construire une base de données afin de développer une méthode pour la caractérisation de l’endommagement. Cette méthode s’appuie sur ces réponses diagraphiques pour retrouver les paramètres de fissure recherchés (problème inverse). Nous procédons tout d’abord par une analyse préliminaire se basant sur un croisement des informations apportées par les différentes électrodes de la sonde puis nous optimisons les résultats par la méthode de recuit simulé. La méthode, ainsi développée est ensuite appliquée à un deuxième ouvrage pour en déterminer l’état interne. Ces travaux détectent plusieurs zones endommagées et caractérisent l’une d’elles par une ouverture centimétrique et une extension comprise entre 1.6m et 3.2m.
Ces travaux prometteurs, attestent d’un premier diagnostic interne des ouvrages massifs en béton, un enjeu qui restait sans réponses satisfaisantes jusqu’à maintenant. // Abstract : The aging of concrete structures is a major problem affecting their sustainability and their efficiency. The owner must maintain the structure serviceability and provide cost-effective management. The goal of this work is to provide detailed information about the state of cracking inside the structure in order to assist the owner to meet its commitments.
In this context, this thesis develops a new technology to assess the condition of mass concrete structures. It relies on a non-destructive method based on electrical resistivity measured from surface, known for its sensitivity to factors associated with concrete deterioration. However, because of its dependence between the investigation depth and the resolution, the method cannot assess the overall state of a structure. Therefore, it was decided to use the electrical resistivity through preexisting boreholes in the structure (electrical logging). The tool used is a normal probe, which has been traditionally used for oil and hydrogeological exploration. In addition to the investigation in depth via boreholes, this probe can get information over a radius of 3.2m around the borehole. However, as the probing volume of concrete increases, the resolution decreases. Difficulty is to use the exploration abilities of the tool, knowing that the resolution is limited. This is to get around the problem by mastering logging concepts and its new application environment. This thesis is based on a first numerical approach to make corrections on field data and to determine the tool sensitivity with regard to the multi-millimeter and centimeter crack size
damage. This was validated with measurements made on a full-size lock located on the St. Lawrence Seaway. A numerical study of the tool response versus the discontinuities parameters such as the crack aperture, the resistivity contrast between the discontinuity and the concrete, and the extension was done. It allowed building a database used to develop a method for the characterization of the damage. This method is based on the tool responses to find the crack parameters (inverse problem). First, we proceed with a preliminary analysis based on a cross of information provided by the different electrodes of the probe then we optimize the results by the method of simulated annealing. The characterization method is applied to another structure to quantify its internal state. These studies detect several damaged areas and characterize one of them by a centimeter aperture and an extension between 1.6m and 3.2m.
This work attest to a first internal diagnosis of massive concrete structures, an issue that
remained without satisfactory answers so far.
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Natural and Controlled Source Magnetotelluric Data Processing and ModelingShan, Chunling January 2014 (has links)
In this thesis, four studies using different geophysical electromagnetic methods are presented. In the first study dealing with airborne measurements, the noise response due to the rotation of the aircraft and the aircraft itself as a metallic conductive body on the Earth's electromagnetic response in very low frequency and low frequency band was investigated. The magnetic fields are independent of the aircraft in the VLF band and part of the LF band. But at higher frequencies (above 100 kHz), the signals are more influenced by the aircraft. The aircraft also generates its own noise frequencies which are mixed with the radio transmitter signals. The second and third studies are applications of radio-, controlled source-magnetotellurics and electrical resistivity tomography methods at a quick-clay landslide site in southwest Sweden. The data are processed and modeled in 2D and 3D, and the models are compared with high-resolution seismic and geotechnical data. The obtained results were further validated and refined by performing synthetic tests in the second study. The third study shows that the 3D models provide larger and more continuous volume of the quick clay structure than traditional 2D models. Both studies have shown that integrated application of geophysical methods for landslides is ideal. Quick clays often overlie the coarse-grained layers showing an increase of resistivity values in the models. In the fourth study, a new audio magnetotelluric data acquisition technique is developed and is named moving magnetotellurics (MMT). In this new technique, the magnetic sensors are placed on the ground and only 15 to 20 minutes data are acquired for each station, which usually is enough to cover the frequency range 30-300 Hz. The new technique is more efficient and convenient than the traditional magnetotelluric method, and test measurements have shown that it is an applicable method in shallow depth studies.
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Groundwater occurrence and quality in Bulawayo province, ZimbabweNygren, Anton, Nordenskjöld, Edvard, Östblom, Erik January 2016 (has links)
This study focused on determining the groundwater flow paths in the crystalline subsurface rocks of the Bulawayo metropolitan, Zimbabwe, through analysing the discontinuities of the electrical properties of the ground, as well as in the magnetic field of the underlying rocks. Further, borehole water quality was analysed by measuring and mapping several chemical parameters, specifically TDS, salinity and the electrical conductivity. The electrical and magnetic anomalies were measured at two field sites within the Bulawayo province, the Harry Allen Golf Course and the Barbour Fields dumpsite, while 120 boreholes were sampled for water quality in a large part the province. Two magnetometers were used to measure the magnetic field and the time and location of the measurements, which resulted, after processing in SURFER, into the magnetic field map of these areas. This was used, in conjunction with the geologic map of the Bulawayo province, in order to determine useful locations for the electrical resistivity surveys. These included electrical resistivity tomography and vertical electrical sounding and were performed with an earth resistivity/induced polarization (IP) meter in order to measure the electrical resistivity of the ground. Inverse modelling was used in the RES2DINV software program to produce the topographic image of resistivity. The results for the borehole sampling showed that the maps for the three chemical parameters were very similar, with the western and northern parts of the mapped area displaying higher concentration values. The results of the electrical resistivity surveying showed probable areas of groundwater flow with its relationship to electric conductivity.
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Geofyzikální průzkum podzemních dutin na lokalitě Letonice / Geophysical survey of subsurface voids at locality LetoniceBartášková, Lucie January 2015 (has links)
The Větrníky national nature reserve, located in the South Moravian region north of the village of Letonice, is one of the largest steppe reserves in Southern Moravia. This whole area is characterized by the presence of both stable and active landslides, and the occurrence of suffosion sinkholes has been monitored there in the long-term. The aim of the thesis was to investigate whether it was possible to observe subsurface phenomena, caused by the washing out of fine rock particles by ground water, by means of geophysical methods. This phenomenon is known as suffosion. The measurements took place in the areas where the suffosion manifestation was very distinctive, that is around two sinkholes that were visible on the surface. In order to identify the suffosion structural-geological causes and their manifestations at a given location, the gravimetric and electrical resistivity tomography (ERT) methods were used in the first stage of the research. Measured data was further processed and geologically interpreted. The gravimetric method has proved suitable when identifying rocks affected by suffosion, in which case we assume that their density is lower than the density of the surrounding rocks. Using the ERT method, it was possible, in the vertical profile, to distinguish the sandy-gravelly sediments...
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Dépôt chimique en phase vapeur d'Al, Cu et Fe en vue d'élaboration de films composés de phases intermétalliques / Chemical vapor deposition of Al, Cu and Fe in view of the processing of intermetallic phases containing filmsAloui, Lyacine 02 October 2012 (has links)
Des films et revêtements composés de phases et composés intermétalliques présentent des propriétés et des combinaisons de propriétés attractives qui ne sont que très partiellement explorées aujourd’hui. Ils sont porteurs de solutions potentielles pour conférer à des matériaux avancés des multifonctionnalités nécessaires dans pratiquement toutes les industries manufacturières et deviennent ainsi source de rupture et d’innovation. Cette situation prévaut pour le système Al-Cu-Fe, au sein duquel même les binaires à base d’Al présentent des propriétés remarquables. Si des techniques de dépôt physique en phase vapeur sont le plus souvent utilisées pour l’élaboration de tels films et revêtements métalliques, l’utilisation de procédés de dépôt chimique en phase vapeur à partir de précurseurs métalorganiques (MOCVD) permettrait à terme le traitement et la fonctionnalisation de surfaces de géométrie complexe. Le présent travail s’inscrit dans cette logique. Il vise la mise au point de procédés MOCVD de films d’Al, de Cu et de Fe. Ces procédés doivent être compatibles afin de constituer la base pour l’élaboration de protocoles complexes permettant le codépôt ou le dépôt séquentiel de ces éléments. La MOCVD d’Al à partir de dimethylethyl amine alane (DMEAA) a été adaptée pour satisfaire les contraintes de codépôt, pour valider le dispositif expérimental utilisé pour le dépôt des films unaires et binaires, pour valider certains aspects mécanistiques du dépôt et pour illustrer la capacité de la technique de couvrir de manière conforme des surfaces de géométrie complexe. Le protocole mise au point permet d’opérer à une pression de 10 Torr, dans une fenêtre de températures entre 160 °C et 240 °C. La modélisation du procédé permet son optimisation dans ces conditions, conduisant à des films d’épaisseur uniforme sur une surface de diamètre 58 mm. La microstructure désordonnée des films est améliorée par un prétraitement plasma des substrats d’acier 304L in situ avant dépôt.Le besoin d’utiliser des précurseurs de Cu et de Fe exemptes d’oxygène (en vue d’un codépôt avec Al) a conduit à tester pour ces deux éléments la famille originale des composés moléculaires à base de ligands amidinates. Il est montré que des films purs de Cu sont obtenus entre 200 °C et 350 °C à partir de [Cu(i-Pr-Me-AMD)]2 dans une phase gazeuse riche en hydrogène, la limite entre les régimes cinétique et diffusionnel étant à 240 °C. Le criblage de précurseurs analogues pour Fe a révélé que, dans les mêmes conditions, le composé [Fe(tBu-MeAMD)2] conduit à des films contenant Fe, Fe4N ainsi qu’à des carbures Fe3C et Fe4C.Des bicouches de Cu et Al ont été déposées à partir des protocoles mis au point. Leur recuit post dépôt a été suivi in situ par diffraction de rayons X et par mesure de la résistance électrique. Il a permis de stabiliser des phases θ-Al2Cu, η-AlCu et, pour la première fois reportée dans la littérature, de la phase approximante γ-Al4Cu9. Il a été démontré que la technique MOCVD associée avec des recuits post dépôt est une méthode appropriée pour obtenir des films composés d’alliages intermétalliques. Des dépôts conformes de tels films peuvent ainsi être envisagés pour des nombreuses applications. / Films and coatings intermetallic phases and intermetallic compounds present proprieties and combination of proprieties which are just partially explored today. They carry potential solutions to confer multifunctionality for advanced materials needed by industries and become a source of disruption and innovation. This situation prevails for the Al-Cu-Fe, in which even the binary Al-based exhibit remarkable properties. While techniques of physical vapor deposition are most often used for the development of such films and metallic coatings, the use of processes of chemical vapor deposition from metallorganic precursors (MOCVD) lead to the treatment and functionalization of surfaces with complex geometry. The present work joins in this logic.It aims at the development of MOCVD processes of Al, Cu and Fe films. These processes must be compatible to constitute the base for the elaboration of complex protocols allowing the codeposition or the sequential deposition of these elements. The MOCVD of Al from dimethylethyl amine alane (DMEAA) was adapted to satisfy the constraints of codeposition to validate the experimental device. Used for the deposition of unary and binary films, to validate certain aspects mechanistic of the deposition and to illustrate the capacity of the technique to cover in a shape way surfaces of complex geometry. The protocol development allows to operate at pressure of 10 Torr, in a window of temperatures between 160 °C and 240 °C. The modeling of the process allows its optimization in these conditions, leading to films with uniform thickness. The disorderly microstructure of these films is improved by a plasma pretreatment of the substrate of 304L steel in situ before deposition. The need to use precursors of Cu and Fe-free oxygen (for a co-deposition with Al) has led to testing for these two elements the original family of molecular compounds based ligands AMIDINATES. It is shown that pure Cu films are obtained between 200 ° C and 350 ° C from [Cu (i-Pr-Me-AMD)]2 in a gaseous phase rich in hydrogen, the boundary between the kinetic schemes and diffusion regyme being at 240 ° C. Screening similar to Fe precursors revealed that, under the same conditions, the compound [Fe (tBu-MeAMD)2] leads to films containing Fe, as well as Fe4N carbides Fe3C and Fe4C. Bilayers of Cu and Al were deposited from the protocols developed. Their post deposition annealing was followed by in situ X-ray diffraction and by measuring the electrical resistance. It has stabilized θ-Al2Cu, η-AlCu phases and, for the first time reported in the literature, the approximant phase γ-Al4Cu9. It was demonstrated that the MOCVD technique associated with post-deposition annealing is a suitable method to obtain films composed of intermetallic alloys. Deposits conform such films can thus be considered for many applications.
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