abstract: ABSTRACT Along with the fast development of science and technology, the studied materials are becoming more complicated and smaller. All these achievements have advanced with the fast development of powerful tools currently, such as Scanning electron microscopy (SEM), Focused Ion Beam (FIB), Transmission electron microscopy (TEM), Energy dispersive X-ray spectroscopy (EDX), Electron energy loss spectroscopy (EELS) and so on. SiTiO3 thin film, which is grown on Si (100) single crystals, attracts a lot of interest in its structural and electronic properties close to its interface. Valence EELS is used to investigate the Plasmon excitations of the ultrathin SrTiO3 thin film which is sandwiched between amorphous Si and crystalline Si layers. On the other hand, theoretical simulations based on dielectric functions have been done to interpret the experimental results. Our findings demonstrate the value of valence electron energy-loss spectroscopy in detecting a local change in the effective electron mass. Recently it is reported that ZnO-LiYbO2 hybrid phosphor is an efficient UV-infrared convertor for silicon solar cell but the mechanism is still not very clear. The microstructure of Li and Yb co-doped ZnO has been studied by SEM and EDX, and our results suggest that a reaction (or diffusion) zone is very likely to exist between LiYbO2 and ZnO. Such diffusion regions may be responsible for the enhanced infrared emission in the Yb and Li co-doped ZnO. Furthermore, to help us study the diffusion zone under TEM in future, the radiation damage on synthesized LiYbO2 has been studied at first, and then the electronic structure of the synthesized LiYbO2 is compared with Yb2O3 experimentally and theoretically, by EELS and FEFF8 respectively. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2013

Mankind makes extensive use of crude oil to fuel its insatiable demands for energy and hydrocarbon derivatives. The refining of crude oil is based on a process known as cracking, where long-chain hydrocarbons are systematically broken into smaller chain hydrocarbons known as fractions with each fraction allowing for the production of a specific material. The maximum efficiency of cracking can be achieved in the petroleum refining processes by controlling the operating parameters of the units, and over the years many studies have attempted to optimize the cracking conditions such as temperatures, pressures and the use of a variety of catalysts to reach maximum productivity. Catalysts such as the Y-type zeolite catalysts are often used because their acidity and thermal stability makes them an ideal cracking catalyst; however the developments of enhanced catalytic properties for zeolite-Y catalysts are essential to increase the production yields. Optimization of the Y-type zeolite catalyst is the focus of this research and accordingly the synthesis, characterization, modifications and catalysis have been studied in depth. A review of the literature has shown that there are three main techniques used to improve the zeolite properties following the synthesis process; (Cation exchange, Dealumination and Desilication), since the crystalline structure of a Y-type zeolite is prepared from an alkaline aluminosilicates gel. However, the literature focuses mainly on the reaction variables used in the modifications. As such this study focuses on the effects of treatment processes on the composition, behaviour and catalytic properties of the synthesized Y-zeolite framework. Laboratory experimental data has confirmed that a synthesis process using 24 h aging for crystal nuclei at 25 °C and 18 h crystallization time for crystal growth at 100 °C produced the desired zeolite NaY morphology, and NaNH4Y zeolite forms with various cation contents (3, 1.5 and 0.5 wt% Na+) were obtained by subjecting the NaY form to a multi-stage ion exchange using 0.5 M NH4NO3 at 80 °C, while the HY form was obtained by the calcination of NH4Y form under high temperature. Calcination temperatures above 450 °C were shown to indicate a removal of the framework hydroxyl groups via dehydroxylation, which led to a collapse of zeolite-Y structure, whereas raising the level of Na+ inside the zeolite lattice throughout the calcination was led to a delay in the starting point of the dehydroxylation region as confirmed via TG and DSC-analyses. This finding was also used in the preparation of the USY form by steaming the HY form, as the former is a traditional zeolite-Y form utilized in the refining units. It was found that Na-ions hindered the extraction of Al-atoms from the Y-lattice thus reducing the rate of dehydroxylation, and minimising rapid contraction of the unit cells and Y-structure collapse, which helped make a rigid structure and a more resilient lattice for steaming at high temperature. In addition, analyses data confirmed that the extraction of EFAl-species from the USY-structures using an EDTA chemical treatment led to an increase in the acidity of treated catalyst and the introduction of mesopores. Lower lattice Si/Al ratio and larger porosity were also found using the dealuminated-desilicated rather than the desilicated-dealuminated leaching method in the treatment of both Y and USY structures via dislodgement of both Si and Al-atoms in NaOH and HCl solution. Cracking was performed on deactivated catalysts (450 °C) in a PFTR using nC7 in N2 at 325 - 425 °C and W/F = 22 - 44 g.h.mol-1, and confirmed that the tuned steaming/leaching conditions succeeded in modifying the catalytic properties of the in house made catalysts, as they possess superior performance when compared to the industrial catalysts typically used.

Dans le présent travail, nous avons étendu aux solvants organiques notre méthodologie radiolytique de synthèse de polymères conducteurs (PCs), initialement développée en solutions aqueuses. Dans ce contexte, la polymérisation des PCs a été étudiée par radiolyse gamma dans différents solvants organiques et sous différentes conditions expérimentales. La synthèse radio-induite a, en particulier, été optimisée dans le dichlorométhane grâce à la variation et à l’ajustement de différents paramètres : atmosphère, dose, débit de dose, concentration des monomères, etc. Cette synthèse a ainsi pu mener à la préparation de différents types de polymères conducteurs : poly (3,4-éthylènedioxythiophène), poly (3-thiophène acétique acide) and Poly (3-hexylthiophène). Ces derniers ont été totalement caractérises en solutions ou après dépôt par des techniques analytiques, spectroscopiques et microscopiques complémentaires. Nous avons en particulier démontré la simplicité et la versatilité de la polymérisation radio-induite de TAA que ce soit dans le dichlorométhane ou dans l’eau, et avons mis en évidence quelques différentes notable entre ces deux voies de synthèse. Nous avons, par ailleurs, évalué l’influence de la nature des espèces radiolytiques oxydantes générées dans le dichlorométhane, via la variation de l’atmosphère de travail (N₂, air ou O₂), sur les propriétés des polymères conducteurs radio-synthétises, en particulier dans le cas de P3HT. Parmi les nombreuses propriétés physiques chimiques que nous avons sondées dans le cas de tous nos polymères conducteurs radio- synthétises les propriétés électroniques et électrochimiques ont fait l’objet d’une attention particulière. Nos matériaux ont alors été incorporés au sien de cellules solaires à pérovskite hybrides organiques-inorganique (PSCs) et y ont été utilisés comme matériaux de transport de trous (HTMs). Notre nouvelle stratégie radiolytique de synthèse décrite et étendu dans le présent manuscrit, ouvre sans aucun doute la voie à la préparation de nouveaux PCs nanostructurés, de morphologie contrôlée et aux propriétés augmentées : par exemple grâce à l’utilisation d’une polymérisation en microémulsions ou par le développement d’une copolymérisation raisonnée. / The extension of our original radiolytic methodology to the use of organic solvents was an important alternative approach to radiation-induced polymerization of conducting polymers (CPs) in aqueous solutions. The polymerization of CPs was studied by using gamma-radiolysis of several organic solvents under different environmental conditions. The optimization of the synthesis conditions of CPs was then conducted into dichloromethane solvent. After optimization of the synthesis conditions (atmosphere, dose, dose rate, concentration of organic monomers, etc.), the use of dichloromethane radiolysis was successfully employed to synthesize various types of conducting polymers: Poly (3,4-ethylenedioxythiophene) (PEDOT), Poly (3-thiophene acetic acid) (PTAA) and Poly (3-hexylthiophene) (P3HT). The radio-synthesized polymers were fully characterized in solution and after deposition by complementary analytical, spectroscopic and microscopic techniques. Also, the simplicity and versatility of radiation induced polymerization of 3-thiophene acetic acid in dichloromethane and in aqueous solutions was demonstrated. The differences between the two radiolysis routes were highlighted. Furthermore, the influence of generating different oxidizing species under different atmospheres (N₂, air or O₂) upon ɣ-irradiation of dichloromethane solutions containing organic monomers was also studied in particular in case of P3HT. The electronic and electrochemical properties were checked for all radio-synthesized CPs. Accordingly, these polymers were then incorporated in hybrid organic and inorganic perovskite solar cells (PSCs) and used as hole transport materials (HTMs). Our new radiolytic strategy described and extended in this manuscript opens the way for the preparation of new nanostructured CPs with controlled morphology and enhanced properties by using microemulsion polymerization and also for the preparation of processable conjugated materials through copolymerization.

Indiana University-Purdue University Indianapolis (IUPUI) / Metal 3D printing typically requires high energy laser or electron sources. Recently, 3D printing using metal filled filaments becomes available which uses PLA filaments filled with metal powders (such as copper, bronze, brass, and stainless steel). Although there are some studies on their printability, the detailed study of their sintering and characterizations is still missing. In this study, the research is focused on 3D printing of bronze filaments. Bronze is a popular metal for many important uses. The objectives of this research project are to study the optimal processing conditions (like printer settings, nozzle, and bed temperatures) to print bronze metal filament, develop the sintering conditions (temperature and duration), and characterization of the microstructure and mechanical properties of 3D printed specimens to produce strong specimens. The thesis includes three components: (1) 3D printing and sintering at selected conditions, following a design of experiment (DOE) principle; (2) microstructure and compositional characterizations; and (3) mechanical property characterization. The results show that it is feasible to print using bronze filaments using a typical FDM machine with optimized printing settings. XRD spectrums show that there is no effect of sintering temperature on the composition of the printed parts. SEM images illustrate the porous structure of the printed and sintered parts, suggesting the need to optimize the process to improve the density. The micro hardness and three-point bending tests show that the mechanical strengths are highly related to the sintering conditions. This study provides important information of applying the bronze filament in future engineering applications.

Thesis advisor: Dunwei Wang / Metal organic frameworks (MOFs) are a class of compounds that show promising potential for a variety of applications due to their uniformity, highly porous structure, lack of dead volume, and fine-tunability. One of these significant applications is in selective ion transport, which makes MOF films a uniquely good separatory material for dual-electrolyte setups, such as those being investigated with Mg-Br batteries. This research has important environmental and industrial ramifications, considering the various drawbacks associated with commercially available batteries such as the lithium-ion battery. The MOF investigated was Mg-MOF-74, which showed promising selective Mg2+ transport abilities. Both Mg-MOF-74 powder and films were synthesized via a vapor-assisted conversion process to maximize efficiency. To characterize the MOF, XRD and SEM imaging was used. This allowed us to gain a nuanced understanding of the material and its properties for further applications. / Thesis (BA) — Boston College, 2022. / Submitted to: Boston College. College of Arts and Sciences. / Discipline: Departmental Honors. / Discipline: Chemistry.

<p> A number of new ternary borate compounds have been synthesized, and their crystal structures have been characterized via X-ray and neutron diffraction techniques. A series of new compounds with the composition PbMBO4 (M = Cr, Mn, Fe, Ga) has been prepared from solid-state reactions and from single crystal growths using PbO as a flux. They crystallize in the orthorhombic Pnma space group and represent a new structure-type for the family of anhydrous borates. The PbAlBO4 compound undergoes a phase transformation at high temperatures, which has been investigated by in-situ powder neutron diffraction experiments. The structure of β-PbAlBO4 has been solved from powder X-ray diffraction data and subsequently confirmed by a Rietveld refinement of powder neutron diffraction data. The investigation of the SrO - Ga2O3 - B2O3 system has led to the synthesis of a new structure-type, SrGaBO4, from solid-state reactions. Its crystal structure has been determined from powder X-ray diffraction data. It crystallizes in the orthorhombic Pbam space group, and is structurally related to the previously known alumino-borate compounds, SrAlBO4 and CaAlBO4. The "Ba2Ti2B2O9" compound has been re-formulated as Ba3Ti3B2O13, and its crystal structure has been determined by single crystal X-ray diffraction. This compound crystallizes in the non-centrosymmetric P6 2m space group. It is isostructural with K3Ta3B2O12 and the high temperature phase of K3Nb3B2O12.</p> / Thesis / Master of Science (MSc)

No / This paper reports on the advancement in the research and development of aeronautical satellite communications within the EU framework. Starting from key aspects such as spectrum regulatory and marketing issues which affect the development of aeronautical communication systems, discussion on the motivation behind the two EU projects, ABATE and WirelessCabin and their interconnection then follows. ABATE concentrated on the development of an aeronautical communications system for flight routes in the European and Northern Atlantic regions. The enabling technology considered in ABATE is discussed. Major achievements and results obtained in the project are reported in this paper. These include the development of a powerful software tool based on a logical design methodology for aeronautical satellite communication systems as well as the characterization of the aeronautical channel through a series of channel measurement campaign and a demonstration of in-flight multimedia satellite communication. The evolvement from ABATE to WirelessCabin is then highlighted. The main objective and current development of WirelessCabin since the start of the project are presented. In particular, issues on electromagnetic compatibility between different electronic equipments on board the aircraft cabin are discussed. Networking aspects for mobility, QoS and VPN support are studied. Specifically, different scenarios for the location management and address assignment schemes for mobility and VPN support are discussed in detail.

Les composés III-N, et le Nitrure de Gallium (GaN) en particulier, sont devenus des matériaux semi conducteurs importants pour l’ensemble de l’humanité. Depuis la fin des années 1990, ils ont permis le développement de composants électroluminescents fiables, diodes LED et diodes laser, qui constituent une solution de remplacement à rendement énergétique amélioré par rapport aux composants à incandescence. Il est possible qu’ils jouent aussi un rôle dans les nouvelles générations de composants pour l’électronique de puissance. Lors du développement des composants, des recherches expérimentales permettent de trouver assez rapidement des solutions pour réaliser les briques technologiques indispensables, mais le temps manque pour comprendre les mécanismes physiques mis en jeu. Nos travaux ont eu pour objectif d’approfondir la compréhension de l’influence de la structure physico-chimique sur les propriétés électriques des contacts ohmiques et Schottky sur GaN de type N. / Group III nitride semiconductor materials (III-N), and especially gallium nitride (GaN), are now key materials for the whole human kind. Since years 1990, reliable and energy-efficient light emitting devices have been developed based on III-N compounds providing higher efficiency replacement solutions to incandescent bulbs. The same III-N materials may also provide higher performance device solutions for power electronics, allowing multi-functional on-chip integration. During the industrial development of devices, experimental work is focused on finding rapidly good enough solutions for each technology brick, and on the eventual integration of the bricks into a complete device processing flow. Very often, little time and effort can be devoted to the understanding of the underlying physical and chemical processes. The aim of this work has been to study the influence of the physical and chemical material structures on the electrical properties of metal - GaN Ohmic and Schottky contacts.

The results presented in this dissertation refer to the geometry of Minkowski spaces, i.e., of real finite-dimensional Banach spaces. First we study geometric properties of radial projections of bisectors in Minkowski spaces, especially the relation between the geometric structure of radial projections and Birkhoff orthogonality. As an application of our results it is shown that for any Minkowski space there exists a number, which plays somehow the role that $\sqrt2$ plays in Euclidean space. This number is referred to as the critical number of any Minkowski space. Lower and upper bounds on the critical number are given, and the cases when these bounds are attained are characterized. Moreover, with the help of the properties of bisectors we show that a linear map from a normed linear space $X$ to another normed linear space $Y$ preserves isosceles orthogonality if and only if it is a scalar multiple of a linear isometry. Further on, we examine the two tangent segments from any exterior point to the unit circle, the relation between the length of a chord of the unit circle and the length of the arc corresponding to it, the distances from the normalization of the sum of two unit vectors to those two vectors, and the extension of the notions of orthocentric systems and orthocenters in Euclidean plane into Minkowski spaces. Also we prove theorems referring to chords of Minkowski circles and balls which are either concurrent or parallel. All these discussions yield many interesting characterizations of the Euclidean spaces among all (strictly convex) Minkowski spaces. In the final chapter we investigate the relation between the length of a closed curve and the length of its midpoint curve as well as the length of its image under the so-called halving pair transformation. We show that the image curve under the halving pair transformation is convex provided the original curve is convex. Moreover, we obtain several inequalities to show the relation between the halving distance and other quantities well known in convex geometry. It is known that the lower bound for the geometric dilation of rectifiable simple closed curves in the Euclidean plane is $\pi/2$, which can be attained only by circles. We extend this result to Minkowski planes by proving that the lower bound for the geometric dilation of rectifiable simple closed curves in a Minkowski plane $X$ is analogously a quarter of the circumference of the unit circle $S_X$ of $X$, but can also be attained by curves that are not Minkowskian circles. In addition we show that the lower bound is attained only by Minkowskian circles if the respective norm is strictly convex. Also we give a sufficient condition for the geometric dilation of a closed convex curve to be larger than a quarter of the perimeter of the unit circle.

Slow speed rotating machines are the mainstay of several industrial applications worldwide. They can be found in paper and steel mills, rotating biological contractors, wind turbines etc. Operational experience of such machinery has not only revealed the early design problems but has also presented opportunities for further significant improvements in the technology and economics of the machines. Slow speed rotating machinery maintenance, mostly related to bearings, shafts and gearbox problems, represents the cause of extended outages. Rotating machinery components such as gearboxes, shafts and bearings degrade slowly with operating time. Such a slow degradation process can be identified if a robust on-line monitoring and predictive maintenance technology is used to detect impending problems and allow repairs to be scheduled. To keep machines functioning at optimal levels, failure detection of such vital components is important as any mechanical degradation or wear, if is not impeded in time, will often progress to more serious damage affecting the operational performance of the machine. This requires far more costly repairs than simply replacing a part. Over the last few years there have been many developments in the use of Acoustic Emission (AE) technology and its analysis for monitoring the condition of rotating machinery whilst in operation, particularly on slow speed rotating machinery. Unlike conventional technologies such as thermography, oil analysis, strain measurements and vibration, AE has been introduced due to its increased sensitivity in detecting the earliest stages of loss of mechanical integrity. This programme of research involves laboratory tests for monitoring slow speed rotating machinery components (shafts and bearings) using AE technology. To implement this objective, two test rigs have been designed to assess the capability of AE as an effective tool for detection of incipient defects within low speed machine components (e.g. shafts and bearings). The focus of the experimental work will be on the initiation and growth of natural defects. Further, this research work investigates the source characterizations of AE signals associated with such bearings whilst in operation. It is also hoped that at the end of this research program, a reliable on-line monitoring scheme used for slow speed rotating machinery components can be developed.