Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 151-159). Also available on the Internet.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15646号 / 工博第3304号 / 新制||工||1499(附属図書館) / 28183 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 岡 二三生, 教授 勝見 武, 准教授 木元 小百合 / 学位規則第4条第1項該当

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15647号 / 工博第3305号 / 新制||工||1499(附属図書館) / 28184 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 岡 二三生, 教授 角 哲也, 准教授 木元 小百合 / 学位規則第4条第1項該当

The microstructure, diffusion and phase transformations in aluminum-steel clad sheet were studied within the thesis by means of light optical microscopy, electron microscopy, resistometry and positron annihilation spectroscopy. Results of experimental methods were supplemented by finite element method employed for evaluation of electrical resistivity and simulation of diffusion between steel and aluminum. Several annealing experiments were carried out. The effective interdiffusion coefficient was evaluated by Boltzmann-Matano method from measured concentration profiles through the interface. Formation of an interfacial intermetallic phase was studied and orthorhombic phases Al13Fe4 and Al5Fe2 were identified present in the layer. Surprising results were obtained from the in-situ annealing in TEM (SEM) which go against the results found in a recent literature - the interfacial layer grows towards steel layer.

The goal of this thesis is to use fringe-pattern phase analysis to calibrate the distortion of a camera lens. The benefit of using this method is that the distortion can be calculated using data from each individual pixel and the methodology does not need any model. The phase used to calibrate the images is calculated in two different ways, either utilizing the monogenic signal or through fringe-pattern phase analysis. The calibration approaches were also validated through different methods. Primarily by utilizing the Hough transform and calibrating simulated distortion. The thesis also introduces a validation approach utilizing the phase orientation calculated through the monogenic signal. The thesis also implements different approaches such as flat field correction to limit the impact of the image sensor noise to mitigate the phase noise. It is also investigated which fringe-pattern frequencies are best suited for calibration through comparative analysis. The comparative analysis identified problems with too high and low frequencies of the fringe-patterns when calibrating using fringe-pattern phase analysis.

No description available.

A precise understanding of the fundamental correlation between synthesis, microstructure and physical properties is of vital importance towards rational design of improved functional epitaxial thin films. With the presence of heterogeneous interface and associated inhomogeneous lattice strain, film microstructure becomes sensitive to subtle interfacial perturbations and hence may exhibit intriguing physical properties. Control of the epitaxial film functionality requires accurate knowledge of the actual film chemistry, interfacial defects and associated strain field. This dissertation reports in-depth microstructural characterization of the intrinsic chemical inhomogeneity in selected epitaxial thin films including superconducting Fe1+yTe1-xSex/SrTiO3(STO) heterogeneous systems, the flux-pinning defects at both of conversional YBa2Cu3O7-δ (YBCO)/substrate lateral interfaces and vertical interfaces of YBCO&BaSnO3(BSO) nanocomposite films, and the misfit dislocation core configurations of STO/MgO and MgO/STO heterostructures pair, using the state-of-the-art aberration-corrected scanning transmission electron microscopy (CS-corrected STEM) in combination with geometric phase analysis (GPA). For the first time, the local atomic arrangement of Te and Se as well as interstitial Fe(2) has been clearly revealed in superconducting Fe1+yTe1-xSex/STO epitaxial films. We found that the film growth atmosphere can greatly affect the film stoichiometry, the homogeneity of Se/Te ordering and thus the overall film superconductivity. YBCO/substrate interface mismatch and YBCO&BSO vertical interface contact have been explored through substrate selection and doping-concentration variation. We observed a diverse nature of intrinsic defects in different YBCO/substrate heterosystems; thermal stable defects capable of maintaining individual strain field have been found effective in flux-pinning. Along the vertical heterointerface of YBCO/BSO, misfit dislocations were found throughout the film thickness. It adds another dimension to the flux-pinning landscape design. Four basic misfit dislocation core configurations of a STO/MgO heterosystem have been identified, and found strongly dependent on the actual interface disordering such as substrate atomic-height steps and interdiffussion. To precisely quantify the heterointerface lattice strain, we first conducted systematic investigations on the accuracy of STEM-based GPA. Follow our protocol, 1 pm accuracy has been proven in the STEM fast-scan direction with a spatial resolution less than 1 nm. The effectiveness and reliability of this optimized GPA strain profile were demonstrated in both applications of a relaxed STO/MgO and a partially strained LaAlO3/STO heterointerfaces, respectively.

No description available.

This PhD thesis aims to improve the knowledge on the processes and chemical species in the gas- and particle-phases that are involved in the production of secondary organic aerosol (SOA) from monoterpene oxidation in the atmosphere. A denuder/filter technique that enabled the simultaneous sampling of gaseous and particulate compounds was applied in the present study. The sampling technique was comprehensively characterised and optimised using twelve atmospherically relevant carbonyl compounds. The present study improved the denuder coating procedure and the sampling performance. An additional coating with the derivatisation reagent, 2,4‑dinitrophenylhydrazine (DNPH), reduced the break-through potential (e.g., from 98% to 0.9% for methyl vinyl ketone) and the fraction of carbonyl compounds on the filter material (e.g., from 8.7% to 0% for acetone). Calibration experiments against an aerosol chamber were performed to reduce the relative standard deviation (RSD) of the calibration points in the denuder measurements. The RSDs were reduced by half for acetone, acetaldehyde, methyl vinyl ketone, glyoxal, benzaldehyde and campholenic aldehyde using a XAD‑4/DNPH denuder, and the quantification error was also reduced. This sampling technique was then applied to a series of α- and β-pinene ozonolysis experiments. The present study examined the influence of an OH radical scavenger (CO), and hence the HO2/RO2 ratio, on the SOA formation, product distribution and partitioning behaviour of selected oxidation products in conjunction with different seed particle acidities. It was shown that SOA yields increased by about 8% in α-pinene ozonolysis when CO and acidic seed particles co-existed, whereas only a marginal difference was observed (increase of 2%) for β-pinene compared to neutral seed particles. From the denuder/filter sample analysis, it was possible to tentatively identify a new compound from the α-pinene ozonolysis, i.e., terpenylic aldehyde. Gas- and particle-phase yields were estimated for the first time for this compound (i.e., 1% and 0.4%, respectively). The atmospheric relevance of terpenylic aldehyde was demonstrated based on ambient filter measurements and a possible formation pathway was suggested. Furthermore, the present study provided an additional explanation for enhanced SOA formation when acidic seed particles are used in monoterpene ozonolysis. It was demonstrated that the isomerisation of monoterpene oxides on acidic seed particles leads to the formation of highly reactive SOA precursors, whose subsequent reaction with ozone contributes significantly to SOA formation.

Dans les alliages multiphasés, la cohérence des interfaces entre des phases en désaccord paramétrique génère des champs élastiques internes à longue distance et généralement anisotropes. L'interaction de ces champs affecte fortement la cinétique des transformations de phase diffusives, et influence la forme et l'arrangement spatial des précipités. Dans la microstructure des superalliages monocristallins à base de nickel, obtenue par précipitation de la phase γ’ ordonnée L12 dans la matrice CFC γ, l'élasticité conduit à la formation d'alignements quasi-périodiques des précipités γ’ cuboïdaux. La microstructure γ/ γ’ possède cependant des défauts systématiques d'alignement des précipités: des branches, des macro-dislocations et des motifs en chevrons. Nous nous intéressons à l'origine de ces défauts d'alignement. Nous conduisons des analyses de stabilité de l'arrangement périodique de précipités en interactions élastiques. Contrairement à la stabilité attendue, les calculs semi-analytiques ont révélé l'instabilité de la distribution périodique de précipités γ’ cubiques, vis-à-vis de certains modes de perturbation. Les principales instabilités sont le mode longitudinal [100] et le mode transverse [110], et leur domaine d'instabilité est analysé vis-à-vis de l'anisotropie élastique. Le développement de ces modes instables est étudié par une méthode de champ de phase classique, en simulant l'évolution de microstructures périodiques soumises à des légères perturbations initiales. Nous montrons que l'expression des instabilités d'arrangement procède essentiellement par l'évolution de la forme des précipités, et conduit à la formation de motifs qui ont pu être reliés à des microstructures expérimentales. En particulier, le mode transverse [110] conduit à la formation de motifs en chevrons. Nous étudions l'influence du taux de phase γ’ et de l'inhomogénéité du module élastique C’, et nous montrons le rôle qu'ils jouent dans la stabilisation de l'arrangement périodique. Dans des simulations réalisées dans des études antérieures, la dynamique des défauts est analysée au moyen de paramètres topologiques issus de la phénoménologie des structures hors-équilibre. Au cours d'un recuit isotherme, nous observons que les branches et les macro-dislocations migrent dans la microstructure selon des mécanismes de montée et de glissement. Nous utilisons ensuite une nouvelle formulation des modèles de champ de phase, intrinsèquement discrète, dans laquelle les interfaces sont résolues essentiellement avec un pas de grille sans friction de réseau et avec une invariance par rotation précise. Cette approche, appelée Sharp Phase Field Method (S-PFM), est implémentée sur une grille CFC, et avec une description des quatre variants de translation des précipités γ’. Nous montrons que la S-PFM permet la modélisation de microstructures à grande échelle, avec plusieurs milliers de précipités à deux et trois dimensions, et donne ainsi accès à des informations statistiques sur l'évolution de la microstructure et sur la dynamique des défauts d'alignement. Nous discutons finalement la perspective de modéliser l'évolution de la microstructure γ/γ’ à une échelle supérieure par une description de la dynamique des défauts d'alignement des précipités. / In multiphase alloys, internal elastic fields often arise as a result of a coherently adjusted misfit between the lattices of coexisting phases. Given their long-range and usually anisotropic nature, the interaction of these fields is known to significantly alter the kinetics of diffusion-controlled phase transformations, as well as influence the shapes and spatial arrangement of the misfitting precipitates. In the microstructure of single-crystal nickel-base superalloys, obtained by precipitation of the L12-ordered γ’ phase in the FCC γ matrix, elasticity leads to the formation of nearly periodic alignments of the cuboidal γ’ precipitates. However, the γ/γ’ microstructure systematically displays defects in the precipitate alignment: branches, macro-dislocations and chevron patterns. We first address the question of the origin of these alignment defects. Stability analyses of the periodic arrangement of elastically interacting precipitates are carried out. Contrary to the expected stability, the semi-analytical calculations revealed the periodic distribution of cubic γ‘ precipitates to be unstable against specific perturbation modes. The main instabilities are the [100] longitudinal mode and the [110] transverse mode, and their instability range is analyzed with respect to the elastic anisotropy. The consequences of these unstable modes are investigated using a classic phase field method, by modeling the evolution of periodic microstructures undergoing small initial perturbations. We show the expression of the instabilities mainly proceeds by the evolution of the precipitate shapes, and leads to the formation of patterns which were related to experimental microstructures. Specifically, the [110] transverse instability is responsible for the formation of chevron patterns. The effects of the volume fraction and of an inhomogeneity on the C’ shear modulus on the stability of the arrangement are studied, and we show the role they play in the partial stabilization of the periodic distribution, though the [100] longitudinal mode always remains unstable. In phase field calculations carried out in previous studies, the dynamics of alignment defects are analyzed by means of topological parameters derived from pattern formation theory. During annealing, branches and macro-dislocations were observed to migrate in the microstructure according to climbing and gliding mechanisms. We then use a new formulation of phase field models, intrinsically discrete, in which the interfaces are resolved with essentially one grid point with no pinning on the grid and an accurate rotational invariance. This approach, known as the Sharp Phase Field Method (S-PFM), is implemented on a FCC grid and accounts for the four translational variants of the γ’ precipitates. We show that the S-PFM allows for the modeling of large-scale microstructures, with several thousand precipitates both in two and three dimensions, and provides access to statistical information on the microstructure evolution and on the the dynamics of alignment defects. We finally discuss the perspective of modeling the evolution of the γ/γ’ microstructure at the macroscale by means of a description of the defect dynamics in the precipitate alignments.