Kyle Heller, for the Master of Science degree in Mechanical Engineering, presented on October 2020, at Southern Illinois University Carbondale.MAJOR PROFESSOR: Dr. Kanchan Mondal Using powder X-ray diffraction, a material can have its crystalline structure identified. Powder X-ray diffraction alone is not enough if a material is unknown. Usually the exact chemical formula of the material is known, or a secondary analytical method is used to extract additional data in order to analyze the crystalline structure using Bragg’s law and the interplanar relationships. Secondary analytical methods are not as easy or inexpensive though. Generic values could be placed into the more basic structure types to obtain a rough idea of potential crystal types including space groups for the material based on its diffraction peaks. However, with a material that has an unknown spacing between its atoms (d-spacing) this is harder to implement. Thus, the use of a secondary software was employed to further analyze the possibilities. In this thesis, the software used for data extraction and refining were Expo 2014 and CrystalMaker X paired with CrystalDiffract and the final visualization was achieved using Endeavor. Two different titanium based organic inorganic halide perovskites (Dye 3 and Dye 4) prepared at different temperatures were evaluated to identify the crystallographic structure using only x-ray data available. The crystal parameters were calculated, and potential unit cells were visualized. Both the materials were found to be 4 (ABX3) type perovskites. The organic component for Dye 3 was methyl ammonium ion and that of Dye 4 was formamidinium ion. These perovskites have shown potential for use as sensitizers in visible light photovoltaic cells. It was concluded that Dye 4 was orthorhombic with a space grouping of C m c a (space group 64). The associated values were a = b =7.94 Å and c =11.55 Å. Dye 3 was also found to be orthorhombic with space grouping of P c c n (space group 56) being a better fit than C m c a. The associated values were a=b=16 Å and c=11 Å.

No description available.

Experiments were designed for an undergraduate instrumental analysis laboratory course, two in X-ray diffraction and two in electrochemistry. Those techniques were chosen due their underrepresentation in the Journal of Chemical Education. Paint samples (experiment 1) and pennies (experiment 2) were characterized using x-ray diffraction to teach students how to identify different metals and compounds in a sample. in the third experiment, copper from a penny was used to perform stripping analyses at different deposition times. As the deposition time increases, the current of the stripping peak also increases. the area under the stripping peak gives the number of coulombs passed, which allows students to calculate the mass of copper deposited on the electrode surface. the fourth experiment was on the effects of variable scan rates on a chemical system. This type of experiment gives valuable mechanistic information about the chemical system being studied.

Thesis advisor: Michael J. Naughton / The nanoscale coaxial cable (nanocoax) has demonstrated sub-diffraction-limited optical confinement in the visible and the near infrared, with the theoretical potential for confinement to scales arbitrarily smaller than the free space wavelength. In the first part of this thesis, I define in clear terms what the diffraction limit is. The conventional resolution formulae used by many are generally only valid in the paraxial limit. I performed a parametric numerical study, employing techniques of Fourier optics, to resolve precisely what that limit should be for nonparaxial (i.e. wide angle) focusing of scalar spherical waves. I also present some novel analytical formulae born out of Debye’s approximation which explain the trends found in the numeric study. These new functional forms remain accurate under wide angle focusing and could materially improve the performance, for example, in high intensity focused ultrasound surgery by further concentrating the power distributed within the point spread function to suppress the side lobes. I also comment of some possible connections to the focusing of electromagnetic waves. In the second part of this thesis I report on a novel fabrication process which yields optically addressable, sub-micron scale, and high aspect ratio metal-insulator-metal nanocoaxes made by atomic layer deposition of Pt and Al2O3. I discuss the observation of optical transmission via the fundamental, TEM-like mode by excitation with a radially polarized optical vortex beam. Also, Laguerre-Gauss beams are shown to overlap well with cylindrical waveguide modes in the nanocoax. My experimental results are based on interrogation with a polarimetric imager and a near-field scanning optical microscope. Various optical apparatus I built during my studies are also reviewed. Numerical simulations were used with uniaxial symmetry to explore 3D adiabatic taper geometries much larger than the wavelength. Finally, I draw some conclusions by assessing the optical performance of the fabricated nanocoaxial structures, and by giving some insights into future directions of investigation. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

The commercial CFD software STAR-CCM+ is applied as a RANS solver for comparison with potential flow methods in the calculation of vertical plane radiation and diffraction problems.  A two-dimensional rectangular cylinder oscillating in an unbounded fluid is first considered, and the added mass result shown to agree well with the analytical potential flow solution.  Hydrodynamic coefficients are then determined for the cylinder oscillating in heave and sway about a calm free surface.  Predicted values are observed to coincide with available experimental and linear potential flow results for most amplitudes and frequencies of oscillation examined.   A three-dimensional radiation problem is then studied in which 1-DoF heave and pitch motions are prescribed to the ONR Tumblehome hullform in calm water at zero forward speed and Fn 0.3.  Combinations of amplitude and frequency of oscillation ranging from small to large are considered.  Results are compared with several potential flow codes which utilize varying degrees of linearization.  Differences in the force and moment results are attributed to particular code characteristics, and overall good agreement is demonstrated between RANS and potential flow codes which employ a nonlinear formulation.  The ONR Tumblehome is next held static in incident head waves of small and large steepness and zero forward speed or Fn 0.3.  Force and moment time histories of the periodic response are compared with the same set of potential flow codes used in the radiation problem.  Agreement between potential flow and RANS is reasonable in the small wave steepness case.  For large wave steepness, the nonlinear wave response is seen to be important and the RANS solution does not generally agree well with potential flow results. / Master of Science

L’utilisation de réseaux optiques dans la géométrie de diffraction conique a connu ces dernières décennies un essor remarquable dans les domaines UV et X grâce à ses propriétés particulières: absence de l’écrantage derrière les traits du réseau aux incidences rasantes, faible dispersion angulaire limitant l’étirement temporel, efficacité de diffraction élevée. Son usage s’est imposé pour la monochromatisation d’impulsions ultra-brèves. C’est aussi l’une des deux options retenues par la Nasa pour le spectrographe à réseau de l’Observatoire à rayon X de la future mission Lynx. Ce travail de thèse contribue au développement de méthodes numériques pour modéliser les effets de diffraction par des réseaux dans une géométrie encore peu étudiée sous cet aspect. La complexité de cette étude réside dans le couplage inhérent entre les deux états fondamentaux de polarisation. Du point de vue numérique, il impose un calcul ‘’vectoriel’’, là où, en géométrie classique des calculs scalaires suffisent. Notre travail s’est appuyé sur les méthodes numériques de calcul de diffraction par des structures périodiques déjà développées dans le cadre de la géométrie classique. Ces méthodes sont basées sur la théorie différentielle, qui consiste à propager une série d’ondes planes au travers de la zone modulée. La méthode différentielle employée est complétée par l’usage de l’algorithme de propagation de la matrice réflectivité. On contourne ainsi certains problèmes de convergence. Dans la partie théorique de ce travail, ces algorithmes sont étendus pour s’adapter aux cas de géométrie oblique. Sur cette base théorique, nous avons pu développer un code de calcul, nommé COROX, fonctionnant dans toutes les géométries d’utilisation. Un certain nombre de réseau types ont été étudiés, tant en géométrie oblique que classique, pour mettre en évidence, non seulement les efficacités de diffraction mais encore les effets de polarisation, (paramètres de Stokes et matrice de Müller) ainsi que les phases spectrales. Des propriétés intéressantes ont été remarquées, comme l’existence d’une composante circulaire non négligeable diffractée par réseau lamellaire quand l’onde incidente polarisée à 45° par rapport au plan du réseau. Le comportement de la phase spectrale est également une donnée significative pour une future gestion d’impulsions ultra-brèves. Des mesures de diffraction ont été effectuées sur la ligne Métrologie du Synchrotron SOLEIL, sur un réseau blazé de 150 traits/mm. Un accord raisonnable entre efficacités mesurées et calculées est constaté si l’on tient compte de la forte rugosité du réseau étudié. / The conical geometry of optical grating diffraction has been suggested and studied, in the last 10 years, for cutting edge applications in the VUV and X-ray domains, due to its specific properties such as: absence of screen inside the grating grooves at grazing incidence, low angular dispersion which limits the temporal spread of short pulses, very high diffraction efficiencies. It has been accepted as the first choice technology for VUV short pulses monochromatization. It is also one of the two options selected by NASA, for the grating spectrograph of the future X-ray Observatory of the Lynx mission. This thesis reports our contribution to the development of numerical methods in order to model the effects of diffraction by optical gratings in this still little studied geometry. This study is made more complex by an inherent coupling between the two fundamental polarization modes. From the numerical aspect, it requires performing “vectorial” computations, whereas, in a classical diffraction geometry, scalar computations are sufficient. Our work is based on numerical methods already developed for modeling optical diffraction by periodic structures in the framework of classical geometry. These methods are using on the differential theory, whose main concept is propagating a set of plane waves throughout the modulated area. We use the differential method together with an algorithm of reflectivity matrix propagation. It overcomes some of the convergence issues. In the theoretical part of this work, reflectivity matrix algorithms are extended to the case of oblique geometry. On these theoretical grounds, we developed a computation code, named COROX, which can be applied in any geometry. A number of typical grating cases have been studied, both in the conical and of le classical one. The output is not only the diffraction efficiencies, but also the polarization properties (Stokes parameters, Müller matrix), as well as the spectral phases. Interesting properties have been noticed, such as the presence of a non-negligible circularly polarized component diffracted from a lamellar grating when the incident wave is linearly polarized at 45° from the grating plane. The spectral phase behavior is also a significant data for an eventual shape tayloring of ultrashort pulses. Diffraction efficiency measurements have been performed on the Metrology beamline of Synchrotron SOLEIL, using a 150 lines/mm blazed grating as a test object. A reasonable agreement between measured and computed efficiencies has been obtained, provided that the rather high roughness of this grating is taken into account.

Ce manuscrit a pour sujet principal la diffraction par rayons X des matériaux ondes de densité de charges (ODC). Nous avons étudié le cristal quasi-1D NbSe3 ainsi que le quasi-2D TbTe3. Plusieurs grands instruments ont été utilisés pour cette étude, le synchrotron ESRF de Grenoble sur la ligne ID01 ainsi que le laser à électron libre LCLS à Stanford. Premièrement, grâce à la cohérence du faisceau X à LCLS, nous avons pu observer une perte de cohérence transverse dans NbSe3 lors de l’application d’un courant électrique au-dessus d’un certain seuil ainsi qu’une compression longitudinale de l’ODC. Ensuite, à l’ESRF, nous avons utilisé un faisceau X focalisé au micromètre par une Fresnel zone plate pour scanner l’ODC localement par diffraction sur NbSe3 puis ensuite sur TbTe3. Lorsqu’un courant est appliqué sur l’échantillon, nous avons observé une déformation transverse indiquant que l’ODC est bloquée au niveau de la surface de l’échantillon dans NbSe3. Dans le cas de TbTe3, l’ODC tourne sous courant présentant un cycle d’hystérésis lorsque le courant passe continument de positif à négatif. Nous avons aussi pu constater dans plusieurs régions, toujours pour TbTe3, la création de défauts d’irradiation localisés induisant une compression-dilatation de l’ODC. Dans une dernière partie théorique, nous montrons comment la théorie du transport électrique de l’ODC par un train de solitons portants chacun une charge ainsi que la prise en compte du blocage de l’ODC sur la surface de l’échantillon que nous avons vu expérimentalement permet de comprendre plusieurs mesures de résistivité en fonction des dimensions de l’échantillon trouvées dans la littérature. Nous présentons ensuite plusieurs idées pour expliquer du blocage de l’ODC sur les surfaces au niveau microscopique et proposons l’hypothèse d’une ODC commensurable en surface (et incommensurable dans le volume). / The main subject of this manuscript is the X-ray diffraction of charge density wave (CDW) materials. We studied the quasi-1D NbSe3 crystal and the quasi-2D TbTe3. Several large instruments facilities were used for this study, the ESRF synchrotron in Grenoble on the ID01 line and the LCLS free electron laser in Stanford. First, thanks to the coherence of the X-beam at LCLS, we were able to observe a loss of transverse coherence in NbSe3 when applying an electrical current above a certain threshold as well as a longitudinal compression of the CDW. Then, at the ESRF, we used an X-ray beam focused on the micrometer scale by a Fresnel zone plate to scan the CDW locally by diffraction on NbSe3 and on TbTe3. When a current is applied to the sample, we observed a transverse deformation indicating that the CDW is pinned on the sample surface in NbSe3. In the case of TbTe3, the CDW rotates under current showing a hysteresis cycle when one is continuously changing from positive to negative current. We have also observed in several regions, in TbTe3, the creation of localized irradiation defects inducing a compression-dilation of the CDW. In a last theoretical part, we show how the theory of electric transport in the CDW state by a train of charged solitons, as well as taking into account the CDW pinning on the surface of the sample that we have seen experimentally, allows us to understand several resistivity measurements, found in the literature, made on samples with different dimensions. Finally, we present several ideas for an explanation of the CDW pinning at the surfaces on a microscopic level and propose the hypothesis of a commensurate CDW on the surface (and incommensurate in volume).

No description available.

No description available.

No description available.