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1	Phenomenology And Experimental Observations In High Temperature Ternary Interdiffusion Elliott, Abby Lee 01 January 2004 (has links) A new method to extract composition dependent ternary interdiffusion coefficients from a single diffusion couple experiment is presented. The calculations involve direct determination of interdiffusion fluxes from experimental concentration profiles and local integration and differentiation of Onsager's formalism. This new technique was applied to concentration profiles obtained from selected semi-infinite, single-phase diffusion couple experiments in the Cu-Ni-Zn, Fe-Ni-Al, and Ni-Cr-Al systems. These couples exhibit features such as uphill diffusion and zero flux planes. The interdiffusion coefficients from the new technique along with coefficients reported from other methods are graphed as functions of composition. The coefficients calculated from the new technique are consistent with those determined from Boltzmann-Matano analysis and an alternate analysis based on the concept of average ternary interdiffusion coefficients. The concentration profiles generated from the error function solutions using the calculated interdiffusion coefficients are in good agreement with the experimental profiles including those exhibiting uphill diffusion. The new technique is checked for accuracy and consistency by back-calculating known interdiffusion coefficients; in this exercise, the new method accurately predicts constant diffusivity. After rigorous verification, the new technique is applied to previously unexamined couples in the Ni-Pt-Al system. With Ni as the dependent component, the main coefficients are shown to be relatively constant and the cross coefficients are negative. The interdiffusion coefficient representing the contribution of the concentration gradient of Pt to the interdiffusion flux of Al is relatively large for couples whose Al content is low, indicating that Pt has a significant effect on Al when Al concentration is low. Another important aspect of analyzing diffusional interactions is the movement of single and multi-phase boundaries within a diffusion couple. Phase boundaries for an n-component system are newly classified and boundary movement is analyzed in terms of degrees of freedom. Experimental evidence of a category 2:1 boundary is presented with a solid-to-solid semi-infinite diffusion couple in the Fe-Ni-Al system with two single-phase terminal alloys. The diffusion path for this couple surprisingly passes through the vertex of the equilibrium tie triangle on the phase diagram to exhibit three phase equilibria in a ternary system. Here is shown for the first time experimental verification of this phenomenon. Diffusion Interdiffusion coefficients Phase boundaries Engineering Materials Science and Engineering
2	Accurate Measurements and Modeling of the PpT Behavior of Pure Substances and Natural Gas-Like Hydrocarbon Mixtures Mantilla, Ivan 2012 August 1900 (has links) The scale of the energy business today and a favorable and promising economic environment for the production of natural gas, requires study of the thermophysical behavior of fluids: sophisticated experimentation yielding accurate, new volumetric data, and development and improvement of thermodynamic models. This work contains theoretical and experimental contributions in the form of 1) the revision and update of a field model to calculate compressibility factors starting from the gross heating value and the mole fractions of diluents in natural gas mixtures; 2) new reference quality volumetric data, gathered with state of the art techniques such as magnetic suspension densimetry and isochoric phase boundary determinations; 3) a rigorous first-principles uncertainty assessment for density measurements; and 4) a departure technique for the extension of these experimental data for calculating energy functions. These steps provide a complete experimental thermodynamic characterization of fluid samples. A modification of the SGERG model, a standard virial-type model for prediction of compressibility factors of natural gas mixtures, matches predictions from the master GERG-2008 equation of state, using least squares routines coded at NIST. The modification contains new values for parametric constants, such as molecular weights and the universal gas constant, as well as a new set of coefficients. A state-of-the-art high-pressure, single-sinker magnetic suspension densimeter is used to perform density measurements over a wide range of temperatures and pressures. This work contains data on nitrogen, carbon dioxide, and a typical residual gas mixture (95% methane, 4% ethane, and 1% propane). Experimental uncertainty results from a rigorous, first-principles estimation including composition uncertainty effects. Both low- and high-pressure isochoric apparatus are used to perform phase boundary measurements. Isochoric P-T data can determine the phase boundaries. Combined with density measurements, isochoric data provides isochoric densities. Further mathematical treatment, including noxious volume and thermal expansion corrections, and isothermal integration, leads to energy functions and thus to a full thermodynamic characterization. Thermodynamics PpT data density measurements magnetic suspension isochoric measurements phase boundaries experimental uncertainty energy functions
3	COOLING RATE CONTROLLED RELAXATION AND THE ASSOCIATED CHEMICAL AND STRUCTURAL RESPONSES IN SINGLE CRYSTAL HETEROSTRUCTURES WITH VOLATILE CATIONS Farghadany, Elahe, Dr 23 May 2022 (has links) No description available. Materials Science Thin films PLD (Nd(2/3)−xLi3x□(1/3)−2x )TiO3 Anti-phase boundaries Self-assembly Cooling rates
4	Darstellung und Verwendung von Nucleolipiden zur Lipophilisierung von Nucleinsäuren sowie deren Wechselwirkung und Duplex-Bildung an horizontalen Lipid-Bilayers und Phasengrenzen zur Entwicklung einer neuartigen RNA/DNA-Analytik / Synthesis and Application of Nucleolipids for the Lipophilization of Nucleic Acids and Their Interaction and Duplex Formation at Horizontal Lipid-Bilayers and Phase Boundaries for the Development of a Novel RNA/DNA Analytics Werz, Emma 17 February 2016 (has links) Ziel der vorgestellten Arbeit war die Synthese von Nucleolipiden zur Lipophilisierung von Oligonucleotiden sowie deren Untersuchung im Hinblick auf ihre Wechselwirkung und Duplex-Bildung an horizontalen Lipidmembranen und verschiedenen Phasengrenzen zur Entwicklung eines neuartigen Bio-Chips für die RNA/DNA-Analyse. Mit der Synthese N(3)-prenylierter und 2’,3’-O-ketalisierter Pyrimidinbasen Uridin und Methyluridin wurden Nucleolipid-Bausteine dargestellt, die auch als terminale Kopfgruppen eines Oligonucleotid-Dodecamers den lipophilen Charakter dieser Oligonucleotid-Sequenz erhöhten. Für den Einsatz solcher LONs (Lipo-Oligonucleotide) in einer vereinfachten RNA/DNA-Analytik wurde eine Vielzahl von Lipo-Oligonucleotiden mit diversen Nucleolipid-Kopfgruppen synthetisiert und auf ihr Einlagerungsverhalten in künstliche Lipid-Bilayer untersucht. Fluoreszenz-spektroskopische Untersuchungen zeigten, dass alle Lipo-Oligonucleotide in der Lage sind, sich in künstliche Lipid-Bilayer einzulagern. Abhängig von der Struktur, der Länge und der Anzahl der C-Atom-Ketten dieser lipophilen Anker-Bausteine wurden die Geschwindigkeit und die Festigkeit der Verankerung im Lipid-Bilayer beeinflusst. Des Weiteren wurde die Hybridisierung von LONs mit komplementären Oligomeren an Lipidmembranen untersucht. Es konnte gezeigt werden, dass die im Bilayer verankerten Lipo-Oligonucleotide mit komplementären Oligomeren DNA-Duplexe bilden. Die hybridisierte DNA wurde nicht nur über einen kovalent gebundenen Cy5-Fluorophor am Gegenstrang nachgewiesen, sondern auch über den DNA-Interkalator SYBR Green I (SG). Am Beispiel von zwei Lipo-Oligonucleotiden (LON 20 und 23), die sich schnell und fest in der Bilayermembran verankern, konnte eine spontane Akkumulation dieser LONs an CHCl3/H2O sowie H2O/n-Decan Grenzflächen direkt nach der Probenzugabe beobachtet werden. Diese und andere Ergebnisse stützen den Einsatz von Lipo-Oligonucleotiden als Ziel-Oligomere in einem neuartigen RNA/DNA-Nachweisverfahren an Phasengrenzen. Lipid-Bilayer FCS Lipo-Oligonucleotide Fluoreszenz lipophilisierte DNA Akkumulation Phasengrenzen Diffusionskoeffizient Nucleolipide SYBR Green I Lipophilie DNA-Duplex Diffusionszeit DNA-Interkalator Cy5 DNA-Duplex-Bildung DNA duplex formation Alkylierung 2`,3`-O-Ketale Farnesyl LONs lipid-bilayer FCS lipo-oligonucleotides fluorescence lipophilized DNA accumulation phase boundaries diffusion coefficient nucleolipids SYBR Green I lipophilicity DNA duplex diffusion time DNA intercalator Cy5 alkylation 2`,3`-O-ketals farnesyl LONs 35.78 - Lipide 42.12 - Biophysik 35.65 - Nukleinsäuren 35.66 - Terpene, Steroide, Alkaloide ddc:540 ddc:570
5	Hochtemperaturinduzierte Mikrostrukturänderungen und Phasenübergänge in nanokristallinen, metastabilen und defektbehafteten Aluminiumoxiden Thümmler, Martin 03 December 2024 (has links) Within the collaborative research center SFB 920 “Multifunctional Filters for Metal Melt Filtration”, the thermally induced formation of metastable aluminum oxides and related microstructural changes were investigated. It was confirmed that the γ-Al₂O₃ phase possesses a defective spinel structure containing Al vacancies that preserve the stoichiometry of this phase. The presence of vacancies fragments apparently the γ-Al₂O₃ crystallites into nanocrystalline domains, which are separated by non-conservative antiphase boundaries (APBs) of the type {100} ¼<110>. These APBs form a 3D network that is randomly distributed over all crystallographically equivalent lattice planes. This phenomenon causes a starlike (and hkl-dependent) broadening of the reciprocal lattice points that correspond to the aluminum sublattice. It was shown that the extent of the broadening of the reciprocal lattice points can be predicted by employing the phase shift factors. With increasing degree of the APBs ordering, the initial streaks representing the broadened reflections start to split, forming superstructure reflections. This superstructure of γ-Al₂O₃ is commonly known as δ-Al₂O₃. Between the ordered APBs, the crystal structure of δ-Al₂O₃ is closely related to the crystal structure of monoclinic θ-Al₂O₃. The phase transition of γ-Al₂O₃/δ-Al₂O₃ to θ-Al₂O₃ proceeds via migration of just three Al³⁺ cations to the neighboring tetrahedral and octahedral sites in the cubic close packed (ccp) oxygen sublattice. The general migration vector is ⅛<111> (γ-Al₂O₃). Diffraction effects associated with different intermediate states can be explained by an improper long-range ordering of equivalent APBs or certain Al³⁺ cations and the local formation of θ-Al₂O₃ within the δ-Al₂O₃ superstructure. The formation of θ-Al₂O₃ is accompanied by an increase of the occupancy of the tetrahedral sites in the oxygen sublattice by the Al³⁺ cations. In surrounding local γ-Al₂O₃ domains, however, some cations migrate from the tetrahedral to the octahedral sites. Thus, the local formation of θ-Al₂O₃ is nearly invisible for the ²⁷Al 1D magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Still, it was recognized by the 2D multiple quantum (MQ) MAS NMR spectroscopy. A continuous formation of the θ-Al₂O₃ domains was confirmed by the Raman spectroscopy, X-ray diffraction (XRD) and selected area electron diffraction (SAED). The proposed microstructure and transformation models helped to explain the thermal stabilization of the metastable alumina phases by Si-doping. For investigation of the thermally induced phase transitions in metastable alumina phases, boehmite (γ-AlO(OH)) was chosen as the starting compound. However, the metastable alumina phases were also observed in endogenous inclusions present in solidified steel melts. For identification of these phases, a procedure for reconstruction of spherical Kikuchi maps from recorded EBSD patterns was developed. info:eu-repo/classification/ddc/620 ddc:620 Aluminiumoxide Mikrostruktur Phasenumwandlung Kristallstruktur Stapelfehler

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