In this Master thesis, microwave connections between circuit boards are constructed. The primary frequency band is the X-band (8-12 GHz). The purpose of the connections is to enable a more simple and cheaper way of mounting the circuit boards inside a container. The connections have been designed and evaluated, using different computer programs. A few prototypes have been built and measured. The main goal of this Master thesis was to design a connection, that would be useful in practice. The connections should be easy to manufacture and have a good performance. They should also have a high tolerance for manufacturing errors. The main part of this report contains descriptions of different designs. The designs are presented together with simulated and measured results. The report contains designs based upon coplanar waveguides and a phase shifting technique. The result shows that designs that are using coplanar waveguides are good. The phase shifting technique has some limitations and need to be developed further.

Gegenstand der vorliegenden Arbeit ist die templatgestützte Erzeugung metallischer Stäbchen und Ringstrukturen im Mikrometer- und Nanometerbereich. Derartige Strukturen besitzen vor allem aufgrund ihres außergewöhnlichen Verhaltes gegenüber elektromagnetischen Wellen ein hohes Potential für optische, elektronische, magnetische oder sensorische Anwendungen. Zunächst wird das Vorgehen zur Herstellung mesoskopischer Ringe durch die Infiltration von Kolloidkristallen aus Siliziumdioxid mittels geeigneter Präkursorlösungen detailliert betrachtet. Daraufhin werden Ansätze zur Optimierung einzelner Teilschritte vorgestellt. Im Anschluss erfolgt die Übertragung des Verfahrens auf die Herstellung von Goldringen. Neben der elektronenmikroskopischen Charakterisierung der Proben wird unter anderem durch energiedispersive Röntgenspektroskopie (EDXS), Elektronenrückstreubeugung (EBSD) und Röntgenphotoelektronenspektroskopie (XPS) bestätigt, dass die entstandenen Strukturen aus metallischem Gold bestehen. Ein weiterer Inhalt dieser Arbeit ist die Konzeption und Umsetzung einer Apparatur zur elektrochemischen Erzeugung von mesoskopischen Metallstäbchen im Inneren von porösen Aluminiumoxidmembranen. Im Anschluss wird die Herstellung von Silber- und Goldstäbchen beschrieben. Außerdem wird aufgeführt, wie die sequenzielle Abscheidung der beiden Metalle unter anschließender Auflösung des metallischen Silbers zur Erhöhung der Ausbeute an isolierten Goldstäbchen führt.

Στην παρούσα διδακτορική διατριβή μελετάται η ανάπτυξη λεπτών υμενίων πορωδών ανοδικών οξειδίων του αλουμινίου (αναφέρονται και ως πορώδης ανοδική αλουμίνα) σε υπόστρωμα πυριτίου. Επιπλέον, εξετάζεται η ανάπτυξη εφαρμογών που αφορούν τη χρήση της πορώδους αλουμίνας ως μάσκα και ως μήτρα για την δημιουργία νανονημάτων ή κβαντικών τελειών (νανονησίδων) στο Si. Το πρώτο κεφάλαιο πραγματεύεται τη θεωρία και τους μηχανισμούς που διέπουν την ανάπτυξη πορωδών υμενίων, που προέρχονται από ανοδική οξείδωση (ανοδίωση) τόσο φύλλων αλουμινίου, όσο και υμενίων αλουμινίου σε υπόστρωμα πυριτίου. Επιπροσθέτως, παρατίθεται ο ρόλος που διαδραματίζουν οι ηλεκτροχημικές συνθήκες ανοδίωσης, όπως το pH, η θερμοκρασία και η εφαρμοζόμενη τάση, στα τελικά δομικά χαρακτηριστικά των πορωδών υμενίων. Στο δεύτερο κεφάλαιο παρουσιάζονται τα τεχνολογικά βήματα διεργασιών που αφορούν την προετοιμασία των δειγμάτων τα οποία πρόκειται να ανοδιωθούν, και δίνονται λεπτομέρειες για την πειραματική διάταξη η οποία χρησιμοποιείται κατά την ανοδίωση. Στο τρίτο κεφάλαιο μελετώνται εκτενώς, τρεις παράγοντες που έχουν σημαντική επίδραση στα τελικά δομικά χαρακτηριστικά των πορωδών υμενίων. Κατά τους δύο πρώτους, εξετάζεται η επίδραση του πάχους του προς ανοδίωση υμενίου αλουμινίου πάνω στο Si, καθώς και ο περιορισμός του σε επιφάνειες μερικών τετραγωνικών μικρομέτρων πάνω στο Si, στο μέγεθος και την πυκνότητα των πόρων. Ο τρίτος παράγοντας αφορά το ρόλο της ανοδίωσης του υμενίου του αλουμινίου σε δύο και τρία στάδια σε συνδυασμό με τη χημική εγχάραξή του μετά από κάθε στάδιο ανοδίωσης, στην ανάπτυξη εξαγωνικής συμμετρίας στην κατανομή των πόρων. Το τέταρτο κεφάλαιο, πραγματεύεται την ανάπτυξη εφαρμογών που συνδέονται με τη χρήση της πορώδους αλουμίνας ως μάσκα και ως μήτρα για τη δημιουργία νανοδομών επάνω στο πυρίτιο. Ως εκ τούτου παρουσιάζεται η δημιουργία νανονησίδων Cr, Ti, νανοστηλών Si, και νανονημάτων Au, πάνω στο Si, εφαρμογές στις οποίες τα πορώδη ανοδικά υμένια χρησιμοποιήθηκαν ως ενδιάμεσο στάδιο. Στο πέμπτο κεφάλαιο παρατίθεται η ανάπτυξη διαμέσου της πορώδους αλουμίνας, εξαγωνικά διατεταγμένων νανονησίδων SiO2 στο Si. Επίσης, παρουσιάζεται ο ηλεκτρικός χαρακτηρισμός διατάξεων οι οποίες αποτελούνται από την εν λόγω δομή. Σε ένα επιπλέον βήμα, οι νανονησίδες SiO2 χρησιμοποιούνται για την ανάπτυξη νανοκρυσταλλιτών Si στο εσωτερικό τους μέσω της τεχνικής της ιοντικής σύνθεσης. Τα σημαντικότερα αποτελέσματα και συμπεράσματα που προέκυψαν από την εκπόνηση της παρούσας διδακτορικής διατριβής συνοψίζονται στα εξής: • Βελτίωση της εξαγωνικής συμμετρίας στην κατανομή των πόρων, μέσω ανοδίωσης σε δύο ή τρία στάδια σε συνδυασμό με χημική εγχάραξη του προς ανοδίωση αλουμινίου έπειτα από κάθε στάδιο ανοδίωσης. • Αύξηση της πυκνότητας των πόρων των ανοδικών υμενίων κατά μία τάξη μεγέθους, με περιορισμό του προς ανοδίωση αλουμινίου σε προεπιλεγμένες περιοχές στο Si, επιφάνειας μερικών τετραγωνικών μικρομέτρων. • Ανάπτυξη διατεταγμένων νανοδομών Ti και Cr σε υπόστρωμα Si χρησιμοποιώντας λεπτά υμένια πορώδους αλουμίνας πάνω σε Si. Ιδιαίτερα οι δομές Cr, μπορούν να χρησιμοποιηθούν ως μεταλλική νανοδομημένη μάσκα για την εγχάραξη με ενεργά ιόντα του υποστρώματος Si και τη δημιουργία νανοστηλών Si πάνω σε αυτό. Η δημιουργία νανοστηλών Si, βρίσκει πληθώρα εφαρμογών στη Νανοηλεκτρονική, σε αισθητήρες, Nανοφωτονική, μνήμες κ.τ.λ. • Οι πυκνότητες διεπιφανειακών καταστάσεων που προέκυψαν από τον ηλεκτρικό χαρακτηρισμό της διεπιφάνειας υμενίων πορώδους αλουμίνας με το πυρίτιο, και της διεπιφάνειας πορώδους αλουμίνας – νανονησίδων SiO2 με το πυρίτιο. Οι τιμές που υπολογίστηκαν είναι ενθαρρυντικές, αν ληφθεί υπόψη ο ηλεκτροχημικός τρόπος παρασκευής των εν λόγω σύνθετων υμενίων πάνω στο πυρίτιο. • Ανάπτυξη μεμονωμένων νανοκρυσταλλιτών Si ενσωματωμένων σε νανονησίδες SiO2. Για το σκοπό αυτό συνδυάστηκαν δύο διαφορετικές τεχνολογίες, εκείνη της ιοντικής σύνθεσης και εκείνη της ανάπτυξης νανονησίδων SiO2 διαμέσου λεπτών υμενίων πορώδους αλουμίνας απευθείας σε υπόστρωμα Si. Τέτοιες δομές νανοκρυσταλλιτών έχουν εφαρμογές σε διατάξεις μη πτητικών μνημών, όπου η κατανεμημένη αποθήκευση φορτίου στους νανοκρυσταλλίτες ευνοεί τη χρήση λεπτότερων οξειδίων πύλης και τη δυνατότητα σμίκρυνσης του πάχους των οξειδίων αυτών χωρίς να μειώνεται ο χρόνος αποθήκευσης φορτίου. / In the present thesis, the growth of porous anodic alumina films on Si substrate was studied extensively. Potential applications of porous anodic alumina films formed directly on Si, regarding the use of porous membranes as mask or template for various nanostructures growth directly on Si, are discussed. Chapter one deals with the theory and mechanisms governing porous anodic alumina film growth, either on porous anodic films formed by anodization of aluminum foils, or on porous anodic films developed on Si substrates. Additionally, the effect of different factors (pH, temperature, applied voltage) on the final structural characteristics is presented. In chapter two, the preliminary processing steps regarding sample preparation before the anodization procedure are quoted. Moreover, details about the experimental set-up and the electrochemical conditions used during the sample anodization in the current work are given. In chapter three, the influence of three different factors, in the final structural characteristics, is investigated. Primarily, the impact of the initial aluminum thickness deposited on Si substrate, and secondly the confinement of the aluminum film in areas of a few μm2, in the pore size and pore density are studied. Finally, the influence of the third factor is associated with a three-step instead of a two-step anodization, in combination with an in-between step of aluminum chemical etching, on the ordering and the uniformity of the pores. The deposition of Ti and Cr nanodots arrays on Si, using the porous alumina membrane as a masking layer, is investigated in chapter four. Furthermore, the Ti nanodots are used for the electrodeposition of Au nanodots and nanowires inside the porous alumina films. Additionally, the Cr dots are used as metallic nanostructured mask for the Si etching by reactive ion etching process, that leads to the formation of Si nanopillars on Si substrate. In chapter five the growth of hexagonally ordered SiO2 dots on Si through porous anodic alumina membranes, in various acidic electrolytes, is studied. Moreover, the electrical characterization of the interface of porous alumina film/Si and porous alumina film with SiO2 dots in pore bottoms/ Si is presented. Finally, in the present thesis the technology of fabrication of Si nanocrystals embedded in SiO2 dots arrays through porous alumina membranes on Si substrate is developed for the first time. This was achieved by the combination of ion beam synthesis with the already existing technology of porous anodic alumina growth on Si substrates. The nanocrystals are electrically isolated from the substrate. This technique is promising as an application in non-volatile memory devices. The main achievements accomplished through this study are summarized as follows: • The optimization of pores ordering by developing the porous alumina membrane in two or three processing steps in combination with the chemical etching of Al film, lying above the porous membrane, following each anodization cycle. • The increase of porous density by the confinement of porous alumina film in areas of a few μm2 on Si. • The development of Ti, Cr and nanodots arrays, directly on Si, through porous alumina membranes. The use of Cr nanodots as nanostructured masking layer for the formation of Si nanopillars, formed by etching of Si substrate with RIE, on Si. • The density of interface stages results from the electrical characterization of porous alumina with or without SiO2 dots at each pore bottom, with the Si substrate. The results are encouraging, keeping in mind that the pore membranes and SiO2 dots were electrochemically grown directly on Si substrate. • The development of distinct Si nanocrystalls, embedded in SiO2 dots, combining for the first time two different technologies, that is the fabrication of porous anodic alumina films directly on Si substrate, as well as the ion beam synthesis technique. The proposed technique is promising for the fabrication of non-volatile memory devices.

The submerged entry nozzle (SEN) is used to transport the molten steel from a tundish to a mould. The main purpose of its usage is to prevent oxygen and nitrogen pick-up by molten steel from the gas. Furthermore, to achieve the desired flow conditions in the mould. Therefore, the SEN can be considered as a vital factor for a stable casting process and the steel quality. In addition, the steelmaking processes occur at high temperatures around 1873 K, so the interaction between the refractory materials of the SEN and molten steel is unavoidable. Therefore, the knowledge of the SEN behaviors during preheating and casting processes is necessary for the design of the steelmaking processes  The internal surfaces of modern SENs are coated with a glass/silicon powder layer to prevent the SEN graphite oxidation during preheating. The effects of the interaction between the coating layer and the SEN base refractory materials on clogging were studied. A large number of accretion samples formed inside alumina-graphite clogged SENs were examined using FEG-SEM-EDS and Feature analysis. The internal coated SENs were used for continuous casting of stainless steel grades alloyed with Rare Earth Metals (REM). The post-mortem study results clearly revealed the formation of a multi-layer accretion. A harmful effect of the SENs decarburization on the accretion thickness was also indicated. In addition, the results indicated a penetration of the formed alkaline-rich glaze into the alumina-graphite base refractory. More specifically, the alkaline-rich glaze reacts with graphite to form a carbon monoxide gas. Thereafter, dissociation of CO at the interface between SEN and molten metal takes place. This leads to reoxidation of dissolved alloying elements such as REM (Rare Earth Metal). This reoxidation forms the “In Situ” REM oxides at the interface between the SEN and the REM alloyed molten steel. Also, the interaction of the penetrated glaze with alumina in the SEN base refractory materials leads to the formation of a high-viscous alumina-rich glaze during the SEN preheating process. This, in turn, creates a very uneven surface at the SEN internal surface. Furthermore, these uneven areas react with dissolved REM in molten steel to form REM aluminates, REM silicates and REM alumina-silicates. The formation of the large “in-situ” REM oxides and the reaction of the REM alloying elements with the previously mentioned SEN´s uneven areas may provide a large REM-rich surface in contact with the primary inclusions in molten steel. This may facilitate the attraction and agglomeration of the primary REM oxide inclusions on the SEN internal surface and thereafter the clogging. The study revealed the disadvantages of the glass/silicon powder coating applications and the SEN decarburization. The decarburization behaviors of Al2O3-C, ZrO2-C and MgO-C refractory materials from a commercial Submerged Entry Nozzle (SEN), were also investigated for different gas atmospheres consisting of CO2, O2 and Ar. The gas ratio values were kept the same as it is in a propane combustion flue gas at different Air-Fuel-Ratio (AFR) values for both Air-Fuel and Oxygen-Fuel combustion systems. Laboratory experiments were carried out under nonisothermal conditions followed by isothermal heating. The decarburization ratio (α) values of all three refractory types were determined by measuring the real time weight losses of the samples. The results showed the higher decarburization ratio (α) values increasing for MgO-C refractory when changing the Air-Fuel combustion to Oxygen-Fuel combustion at the same AFR value. It substantiates the SEN preheating advantage at higher temperatures for shorter holding times compared to heating at lower temperatures during longer holding times for Al2O3-C samples. Diffusion models were proposed for estimation of the decarburization rate of an Al2O3-C refractory in the SEN. Two different methods were studied to prevent the SEN decarburization during preheating: The effect of an ZrSi2 antioxidant and the coexistence of an antioxidant additive and a (4B2O3 ·BaO) glass powder on carbon oxidation for non-isothermal and isothermal heating conditions in a controlled atmosphere. The coexistence of 8 wt% ZrSi2 and 15 wt% (4B2O3 ·BaO) glass powder of the total alumina-graphite refractory base materials, presented the most effective resistance to carbon oxidation. The 121% volume expansion due to the Zircon formation during heating and filling up the open pores by a (4B2O3 ·BaO) glaze during the green body sintering led to an excellent carbon oxidation resistance. The effects of the plasma spray-PVD coating of the Yttria Stabilized Zirconia (YSZ) powder on the carbon oxidation of the Al2O3-C coated samples were investigated. Trials were performed at non-isothermal heating conditions in a controlled atmosphere. Also, the applied temperature profile for the laboratory trials were defined based on the industrial preheating trials. The controlled atmospheres consisted of CO2, O2 and Ar. The thicknesses of the decarburized layers were measured and examined using light optic microscopy, FEG-SEM and EDS. A 250-290 μm YSZ coating is suggested to be an appropriate coating, as it provides both an even surface as well as prevention of the decarburization even during heating in air. In addition, the interactions between the YSZ coated alumina-graphite refractory base materials in contact with a cerium alloyed molten stainless steel were surveyed. The YSZ coating provided a total prevention of the alumina reduction by cerium. Therefore, the prevention of the first clogging product formed on the surface of the SEN refractory base materials. Therefore, the YSZ plasma-PVD coating can be recommended for coating of the hot surface of the commercial SENs.

Στόχος της διδακτορικής αυτής διατριβής ήταν η ανάπτυξη μιας μεθόδου παραγωγής νανοσωλήνων άνθρακα η οποία στηρίζεται στη χημική απόθεση ατμών, χρησιμοποιώντας ως πηγή του άνθρακα ενώσεις σε υγρή μορφή, όπως οι αλκοόλες. Επιπρόσθετα μελετήθηκαν διάφορες παράμετροι της πειραματικής διαδικασίας (πηγή άνθρακα, θερμοκρασία απόθεσης, είδος και συγκέντρωση μετάλλου και υποστρώματος, παρουσία υδρογόνου κ.ά), τόσο ως προς την επίδρασή τους στο ρυθμό εξέλιξης της διεργασίας, όσο και ως προς το είδος των παραγόμενων προϊόντων, με σκοπό τη στοχευμένη παραγωγή νανοσωλήνων άνθρακα με συγκεκριμένες ιδιότητες. Η κύρια πειραματική διάταξη αποτελούνταν από έναν θερμοβαρομετρικό αντιδραστήρα, ο οποίος επέτρεπε τη συνεχή μέτρηση των μεταβολών του βάρους του δείγματος σε συνάρτηση με το χρόνο, ενώ και φασματογράφος μάζας ήταν συνδεδεμένος στην έξοδο του αντιδραστήρα για να μελετηθεί η αέρια φάση των αντιδράσεων. Τα προϊόντα προκειμένου να πιστοποιηθούν ως προς το είδος των νανοσωλήνων που παρήχθησαν, χαρακτηρίστηκαν με τη βοήθεια ηλεκτρονικής μικροσκοπίας σάρωσης (SEM) και διερχόμενης δέσμης (TEM), καθώς και με φασματοσκοπία Raman και θερμοσταθμική ανάλυση (TGA). Τα αποτελέσματα των πειραμάτων οδήγησαν στο συμπεράσμα πως οι ατμοί της αιθανόλης είναι καλύτερη πηγή άνθρακα σε σύγκριση με της μεθανόλης, οδηγώντας μάλιστα στη παραγωγή μίγματος πολυφλοιϊκών και μονοφλοιϊκών νανοσωλήνων άνθρακα, με καθαρότητες που ξεπερνούσαν το 90%. Επιτακτική αποδείχθηκε η παρουσία του μετάλλου, το οποίο και αποτελεί το κέντρο πυρημοποιήσης για την ανάπτυξη των νανοσωλήνων, ενώ καθοριστική είναι και η χρήση υποστρώματος προκειμένου ο άνθρακας να αποτεθεί με τη μορφή αυτή. Επιπρόσθετα, η παρουσία του υδρογόνου αύξησε σημαντικά το ποσοστό του άνθρακα που αποτέθηκε οδηγώντας μάλιστα στο σχηματισμό μεταλλικών μονοφλοικών νανοσωλήνων άνθρακα πολύ μικρής διαμέτρου, η οποία υπολογίστηκε ίση με 0.45nm. / The main goal of this research was the development of a new method for the production of carbon nanotubes, based on chemical vapor deposition (CVD), which employs a liquid carbon source. In addition, a detailed investigation of the effect of several parameters (carbon source, deposition temperature, kind and metal concentration and support, hydrogen addition e.t.c.) on both the process and the final carbon product was carried out. For this purpose, a CVD experimental apparatus was developed, which uses vapors of liquid precursors and allows the continuously recording of sample weight changes in correlation with time. In some cases, a mass spectrometer was used as a way to determine the kind of processes that take place in the gas phase during carbon deposition. The solid product was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and thermogravimetric analysis (TGA). The experimental results led to the conclusion that ethanol vapors are preferable because they lead to higher yield of both multi-wall and single-wall carbon nanotubes. Also, it was proved that the presence of a metal catalyst and support is necessary, because the first one is the active site of carbon nanotubes formation, and the second leads to the deposition of carbon in this form. Additionally, it was proved that the use of hydrogen in the gas mixture of the process is very important, as a way to reduce catalyst, leading to the formation of metalic single-wall carbon nanotubes of very small diameter (0.45nm).

Le mécanisme menant à des déformations structurales suivant le bombardement d'échantillons de a-Si d'un faisceau d'ions lourds et rapides est sujet de controverses. Nous nous sommes penchés sur l'hypothèse de la formation d'une zone liquide causée par la déposition d'énergie des ions incidents dans le contexte de la théorie du pic thermique. Des échantillons de silicium amorphe furent préparés dans le but d'observer les indices d'une transition de phase l-Si/a-Si suivant la déposition locale d'énergie sur le parcours d'un ion lourd énergétique dans le a-Si. Les échantillons furent implantés d'impuretés de Cu ou d'Ag avant d'être exposés à un faisceau d'ions Ag12+ de 70 MeV. L'utilisation de l'analyse GISAXS est projetée afin d'observer une concentration locale d'impuretés suivant leur ségrégation sur la trace de l'ion. Des masques d'implantation nanométriques d'oxide d'aluminium ont été fabriqués afin d'augmenter la sensibilité de l'analyse GISAXS et une méthode d'alignement de ces masques selon la direction du faisceau fut développée. Le bombardement d'échantillons au travers de ces masques a donné lieu à un réseau de sites d'impacts isolés presque équidistants. / The machanisms underlying structural deformations following swift heavy ion beam a-Si irradiation are subject of debate. We investigated the hypothesis of the presence of a liquid phase in the wake of the energetic ions in the thermal spike framework. a-Si samples were prepared in order to track a transient liquid phase by implanting Cu or Ag on the a-Si surface and exposing the sample to a 70 MeV Ag12+ beam. Cu and Ag are both very sensitive to segregation in Si and are therefore thought to be capable of keeping track of a molten transient state by concentrating on the ion track. Samples are to be investigated with GISAXS. Nanoscale implantation masks were developed from nanoporous alumina membranes in order to impose a pattern on the ion impact sites and thus improve GISAXS sensitivitity. An alignment method is also developed for the positioning of pores parallel to the ion beam direction. A nearly equidistant impact sites pattern was achieved by irradiating fused silica through these implantation masks.

It is well known that nanostructures possess unique electronic, optical, magnetic, ferroelectric and piezoelectric properties that are often superior to traditional bulk materials. In particular, one dimensional (1D) nanostructured inorganic materials including nanofibres, nanotubes and nanobelts have attracted considerable attention due to their distinctive geometries, novel physical and chemical properties, combined effects and their applications to numerous areas. Metal ion doping is a promising technique which can be utilized to control the properties of materials by intentionally introducing impurities or defects into a material. γ-Alumina (Al2O3), is one of the most important oxides due to its high surface area, mesoporous properties, chemical and thermal properties and its broad applications in adsorbents, composite materials, ceramics, catalysts and catalyst supports. γ-Alumina has been studied intensively over a long period of time. Recently, considerable work has been carried out on the synthesis of 1D γ-alumina nanostructures under various hydrothermal conditions; however, research on the doping of alumina nanostructures has not been forthcoming. Boehmite (γ-AlOOH) is a crucial precursor for the preparation of γ-Alumina and the morphology and size of the resultant alumina can be manipulated by controlling the growth of AlOOH. Gallium (Ga) is in the same group in the periodic table as aluminum. β-Gallium (III) oxide (β-Ga2O3), a wide band gap semiconductor, has long been known to exhibit conduction, luminescence and catalytic properties. Numerous techniques have been employed on the synthesis of gallium oxide in the early research. However, these techniques are plagued by inevitable problems. It is of great interest to explore the synthesis of gallium oxide via a low temperature hydrothermal route, which is economically efficient and environmentally friendly. The overall objectives of this study were: 1) the investigation of the effect of dopants on the morphology, size and properties of metal ion doped 1D alumina nanostructures by introducing dopant to the AlOOH structure; 2) the investigation of impacts of hydrothermal conditions and surfactants on the crystal growth of gallium oxide nanostructures. To achieve the above objectives, trivalent metal elements such as iron, gallium and yttrium were employed as dopants in the study of doped alumina nanostructures. In addition, the effect of various parameters that may affect the growth of gallium oxide crystals including temperature, pH, and the experimental procedure as well as different types of surfactants were systematically investigated. The main contributions of this study are: 1) the systematic and in-depth investigation of the crystal growth and the morphology control of iron, gallium and yttrium doped boehmite (AlOOH) under varying hydrothermal conditions, as a result, a new soft-chemistry synthesis route for the preparation of one dimensional alumina/boehmite nanofibres and nanotubes was invented; 2) systematic investigation of the crystal growth and morphology and size changes of gallium oxide hydroxide (GaOOH) under varying hydrothermal conditions with and without surfactant at low temperature; We invented a green hydrothermal route for the preparation of α-GaOOH or β-GaOOH micro- to nano-scaled particles; invented a simple hydrothermal route for the direct preparation of γ-Ga2O3 from aqueous media at low temperature without any calcination. The study provided detailed synthesis routes as well as quantitative property data of final products which are necessary for their potential industrial applications in the future. The following are the main areas and findings presented in the study: • Fe doped boehmite nanostructures This work was undertaken at 120ºC using PEO surfactant through a hydrothermal synthesis route by adding fresh iron doped aluminium hydrate at regular intervals of 2 days. The effect of dopant iron, iron percentage and experimental procedure on the morphology and size of boehmite were systematically studied. Iron doped boehmite nanofibres were formed in all samples with iron contents no more than 10%. Nanosheets and nanotubes together with an iron rich phase were formed in 20% iron doped boehmite sample. A change in synthesis procedure resulted in the formation of hematite large crystals. The resultant nanomaterials were characterized by a combination of XRD, TEM, EDX, SAED and N2 adsorption analysis. • Growth of pure boehmite nanofibres/nanotubes The growth of pure boehmite nanofibres/nanotubes under different hydrothermal conditions at 100ºC with and without PEO surfactant was systematically studied to provide further information for the following studies of the growth of Ga and Y doped boehmite. Results showed that adding fresh aluminium hydrate precipitate in a regular interval resulted in the formation of a mixture of long and short 1D boehmite nanostructures rather than the formation of relatively longer nanofibres/nanotubes. The detailed discussion and mechanism on the growth of boehmite nanostructure were presented. The resultant boehmite samples were also characterized by N2 adsorption to provide further information on the surface properties to support the proposed mechanism. • Ga doped boehmite nanostructures Based on this study on the growth of pure boehmite nanofibre/nanotubes, gallium doped boehmite nanotubes were prepared via hydrothermal treatment at 100ºC in the presence of PEO surfactant without adding any fresh aluminium hydrate precipitate during the hydrothermal treatment. The effect of dopant gallium, gallium percentage, temperature and experimental procedure on the morphology and size of boehmite was systematically studied. Various morphologies of boehmite nanostructures were formed with the increase in the doping gallium content and the change in synthesis procedure. The resultant gallium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • Y doped boehmite nanostructures Following the same synthesis route as that for gallium doped boehmite, yttrium doped boehmite nanostructures were prepared at 100ºC in the presence of PEO surfactant. From the study on iron and gallium doped boehmite nanostructures, it was noted both iron and gallium cannot grow with boehmite nanostructure if iron nitrate and gallium nitrate were not mixed with aluminium nitrate before dissolving in water, in particular, gallium and aluminium are 100% miscible. Therefore, it’s not necessary to study the mixing procedure or synthesis route on the formation of yttrium doped boehmite nanostructures in this work. The effect of dopant yttrium, yttrium percentage, temperature and surfactant on the morphology and size of boehmite were systematically studied. Nanofibres were formed in all samples with varying doped Y% treated at 100ºC; large Y(OH)3 crystals were also formed at high doping Y percentage. Treatment at elevated temperatures resulted in remarkable changes in size and morphology for samples with the same doping Y content. The resultant yttrium doped boehmite nanostructures were characterized by TEM, XRD, EDX, SAED, N2 adsorption and TGA. • The synthesis of Gallium oxide hydroxide and gallium oxide with surfactant In this study, the growth of gallium oxide hydroxide under various hydrothermal conditions in the presence of different types of surfactants was systematically studied. Nano- to micro-sized gallium oxide hydroxide was prepared. The effect of surfactant and synthesis procedure on the morphology of the resultant gallium oxide hydroxide was studied. β-gallium oxide nanorods were derived from gallium oxide hydroxide by calcination at 900ºC and the initial morphology was retained. γ-gallium oxide nanotubes up to 65 nm in length, with internal and external diameters of around 0.8 and 3.0 nm, were synthesized directly in solution with and without surfactant. The resultant nano- to micro-sized structures were characterized by XRD, TEM, SAED, EDX and N2 adsorption. • The synthesis of gallium oxide hydroxide without surfactant The aim of this study is to explore a green synthesis route for the preparation of gallium oxide hydroxide or gallium oxide via hydrothermal treatment at low temperature. Micro to nano sized GaOOH nanorods and particles were prepared under varying hydrothermal conditions without any surfactant. The resultant GaOOH nanomaterials were characterized by XRD, TEM, SAED, EDX, TG and FT-IR. The growth mechanism of GaOOH crystals was proposed.

Ce travail est dédié á l´étude de l´influence de nano-particules de alumina (Al2O3) et de di-borure de titane (TiB2) sur la solidification, la microstructure et les propriétés thermiques et mécaniques de l´alliage d´aluminium renforcés, Al-Si9Cu3Fe1. Les matériaux ont été obtenus par un procédé de fonderie à haute pression en coulant les alliages dans les mêmes conditions que les alliages non renforcés correspondants.On a constaté que les particules de Al2O3 et de TiB2 ont une influence directe sur les caractéristiques de l´alliage telles que la microstructure, la précipitation des phases pendant la solidification et les propriétés mécaniques et électriques. On a ainsi montré que les particules de Al2O3 et de TiB2 peuvent être utilisées pour ajuster les caractéristiques des alliages et obtenir des propriétés spécifiques pour des applications dans les secteurs de matériaux légers. / The work has been focused on the study of the influence of TiB2 and Al2O3 nano-particles (up to 1 wt. %) on the properties and physical features of an aluminium casting alloy, Al-Si9Cu3Fe1.Samples have been obtained through the High Pressure Die Casting (HPDC) process and compared with unreinforced samples obtained at the same conditions. It has been observed that the Al2O3 and TiB2 particles have a direct influence on several features of the alloy such as the microstructure and precipitating phases as well as in the improvement of the soundness and mechanical and electrical properties. Al2O3 and TiB2 particles can be used to tailor the properties of the alloy and to match the specifications of light weight applications

No description available.

Dans le cadre de l'intégration « 3D », une technologie d'assemblage par report de puces sur tranche de silicium (« flip chip ») reposant sur un procédé de microinsertion a été développée ces dernières années. Cette technologie est basée principalement sur la mise en contact par thermocompression, de réseaux de (micro)inserts en Nickel ECD, avec des plots de connexions métalliques en Al(Cu). Au cours de ce travail, un scénario de formation du contact entre un unique microinsert de Nickel rugueux et un film mince d'Aluminium lisse, prenant en compte la présence d'Alumine native à l'interface de contact, est proposé pour une gamme de pressions allant du MPa au GPa. L'analyse du contact métal-oxyde-métal se base essentiellement sur la fissuration de l'oxyde natif suivie de l'extrusion du métal au travers des fissures, et nécessite d'établir au préalable les lois de comportement des matériaux mis en jeu à partir d'essais de nanoindentation instrumentée couplés à des simulations numériques. Enfin, la mesure de l'évolution de la résistance électrique de contact en fonction de la force appliquée à l'aide de dispositifs expérimentaux originaux, permet de mettre en évidence les différents mécanismes de formation du contact métallique lors du procédé de microinsertion. / In the field of « 3D » microelectronic integration, a wafer level technology using flip chip stacking and based on a microinsertion process has been developed recently. This technology is mainly based on the contact realized by thermocompression between a network of microinserts made of Nickel ECD, with connections pads in Al(Cu). In this work, a scenario describing the contact establishment between a unique rough microinsert of Nickel and a smooth thin Aluminum film taking into account the presence of native Alumina at the contact interface, is developed for a range of pressures from MPa to GPa. The analysis of the metal-oxide-metal contact is essentially based on the fracture of the native oxide followd by the metal extrusion through cracks, and requires the knowledge of the behaviour laws of materials, obtained from instrumented nanoindentation tests coupled with numerical modeling. Finally, the measure of the electrical contact resistance evolution in function of applied load, with specific pioneering experimental setup, showcases the mechanisms driving the formation of metallic contact during the microinsertion process.