Magmatic-hydrothermal ore deposits are formed in association with aqueous fluids that exsolve from hydrous silicate melts during ascent and crystallization. These fluids are invariably trapped as inclusions in vein-filling minerals associated with hydrothermal fluid flow, and their composition may be modeled based on the H₂O-NaCl system. Thus, if we know the pressure-volume-temperature-composition (PVTX) properties of H₂O-NaCl solutions, it is possible to interpret the PTX trapping conditions, which is important for understanding the processes leading to the generation of the hydrothermal system and ore mineralization. High salinity (> 26 wt. % NaCl) fluid inclusions contain liquid, vapor, and halite at room temperature, and are common in magmatic-hydrothermal ore deposits. These inclusions homogenize in one of three ways: A) halite disappearance (Tmhalite) followed by liquid-vapor homogenization (ThL-V), B) simultaneous ThL-V and Tmhalite, or C) ThL-V followed by Tmhalite. The PVTX properties of H₂O-NaCl solutions three phase (L+V+H) and liquid-vapor (L+V) phase boundaries are well constrained, allowing researchers to interpret the minimum trapping pressure of inclusion types A and B. However, data that describe the pressure at Tmhalite for inclusion type C are limited to a composition of 40 wt. % NaCl. To resolve this problem, the synthetic fluid inclusion technique was used to determine the relationship between homogenization temperature and minimum trapping pressure for inclusions that homogenize by mode C. These results allow researchers to interpret the minimum trapping pressure of these inclusions, and by extension the depth at which the inclusions formed. The temporal and spatial distribution of fluid inclusions formed in associated with porphyry copper mineralization has been predicted using a computer model. A simple geologic model of an epizonal intrusion was developed based on a Burnham-style model for porphyry systems and thermal models of the evolution of epizonal intrusions. The phase stability fields and fluid inclusion characteristics at any location and time were predicted based on PVTX properties of H₂O-NaCl solutions. These results provide vectors towards the center of a magmatic-hydrothermal system that allow explorationists to use fluid inclusion petrography to predict position with the overall porphyry environment when other indicators of position are absent. / Ph. D.

The system H₂O-CH₄ is found in a variety of geological environments in the earth’s crust, from sedimentary basins to low grade metamorphic terrains. Knowledge of the PressureVolume-Temperature-Composition (PVTX) properties of the H₂O-CH₄ system is necessary to understand the role that these fluids play in different geological environments. In this study the properties of the H₂O-CH₄ fluid system at elevated temperatures and pressures has been investigated experimentally to determine the PVTX properties of H₂O-CH₄ fluids in the P-T range equivalent to late diagenetic to low grade metamorphic environments, and XCH₄≤4mol%. A study has also been conducted to determine methane hydrate stability over the temperature range of -40~20°C. Synthetic fluid inclusions were employed in both studies as miniature autoclaves. Experimental data for the PVTX properties of H₂O-CH₄ fluids under late diagenetic to low grade metamorphic conditions was used to calculate the slopes of isoTh lines (the line connecting the P-T conditions of the inclusions at formation and at homogenization) at different PTX conditions. An empirical equation to describe the slope of iso-Th line as a function of homogenization temperature and fluid composition was developed. The equation is applicable to natural H₂O-CH₄ fluid inclusions up to 500°C and 3 kilobars, for fluid compositions ≤4 mol% CH₄. The Raman peak position of CH₄ gas is a function of the pressure and temperature. This relationship was used to determine the pressure along the methane hydrate stability curve in the H₂O-CH₄ system. The combined synthetic fluid inclusion, microthermometry and Raman spectroscopy method is a novel experimental approach to determine the P-T stability conditions of methane hydrates. The method is fast compared to conventional methods, and has the potential to be applied to study other gas hydrate systems. / Ph. D.

In many geologic environments, fluids have compositions that are approximated by the H₂O-NaCl system. When minerals grow in the presence of such fluids, some of the solution is trapped in the growing mineral as fluid inclusions. The salinity, temperature of homogenization, and pressure of homogenization are required to predict the trapping conditions of the fluid inclusion. In the laboratory the salinity and the temperature of homogenization of the trapped fluid are easily determined however, the pressure of homogenization cannot be determined directly, and must be calculated from an equation of state. A statistical model that relates the vapor pressure of H₂O-NaCl to the fluid temperature and composition has been developed. The model consists of equations that predict the vapor pressure of H₂O-NaCl from the eutectic temperature (-21.2°C) to 1500°C and for all compositions between the pure end-members. The model calculates the vapor pressure based on the composition (wt% NaCl) and the temperature of homogenization, which can be directly obtained from laboratory studies of fluid inclusions. This information in turn can be used to construct the isochore, or line of constant volume, along which the fluid inclusion was trapped. Finally the isochore can be used to determine the temperature and pressure at which the host mineral of the fluid inclusion was trapped. / Master of Science

No description available.

<p>Cilj ove doktorske disertacije je postavljanje<br />matematičkog modela složenog trofaznog reakcionog<br />sistem za epoksidovanje sojinog ulja in situ formiranom<br />persirćetnom kiselinom iz sirćetne kiseline i vodonik<br />peroksida u prisustvu jonoizmenjivačke smole kao<br />katalizatora. Model uzima u obzir koncentracije<br />reaktanata i produkata u vodenoj i uljnoj fazi. Pored<br />osnovnih reakcija stvaranja persirćetne kiseline i<br />epoksida, model obuhvata i sporednu reakciju otvaranja<br />epoksi prstena sa sirćetnom kiselinom. Za modelovanje<br />reakcije formiranja persirćetne kiseline na povr&scaron;ini<br />katalizatora primenjeni su Langmuir-Hinshelwood-<br />Hougen-Watson i Rideal-Eley postulati. Postavljeni<br />trofazni model predstavlja sistem običnih diferencijalnih<br />jednačina prvog reda koji opisuje promenu broja molova<br />komponenata i funkcionalnih grupa sa vremenom<br />izvođenja procesa epoksidovanja, i sadrži vi&scaron;e parametara<br />razvrstanih na kinetičke, termodinamičke i parametre koji<br />se odnose na prenos mase. Parametri modela zavise od<br />uslova izvođenja epoksidovanja i to svi od temperature, a<br />neki i od sastava i inteziteta me&scaron;anja.<br />Za konstantu hemijske ravnoteže reakcije nastajanja<br />persirćetne kiseline je izvedena semiteorijska zavisnost<br />od temperature koja daje vrednosti istog reda veličine i<br />istog smera promene sa temperaturom kao i većina<br />podataka objavljenih u literaturi.<br />Za izračunavanje koeficijenta raspodele sirćetne kiseline<br />između uljne i vodene faze potrebno je odrediti zavisnost<br />konstante fazne ravnoteže tečno-tečno sirćetne kiseline od<br />sastava i temperature. Utvrđeno je da je UNIFAC model<br />grupnih doprinosa za koeficijente aktivnosti nepogodan<br />za predskazivanje ravnoteže tečno-tečno. Eksperimentalni<br />podaci za ovu konstantu ravnoteže su uspe&scaron;no korelisani<br />UNIQUAC modelom za koeficijente aktivnosti.<br />Parametri reparametrizovane Arrheniusove zavisnosti<br />konstanti brzina reakcija i konstanti sorpcije učesnika<br />reakcije stvaranja persirćetne kiseline od temperature<br />određeni su simultano sa parametrima koji se odnose na<br />prenos mase i sa odnosom koeficijenata raspodele<br />persirćetne i sirćetne kiseline između uljne i vodene faze,<br />fitovanjem eksperimentalnih podataka epoksidovanja<br />sojinog ulja, tj. minimizacijom sume kvadrata odstupanja<br />računskih od eksperimentalno određenih vrednosti jodnog<br />broja i sadržaja epoksi kiseonika tokom epoksidovanja.<br />Fitovanje je uspe&scaron;no izvedeno primenom metode<br />Marquardta, dok su pomenute računske vrednosti<br />dobijene numeričkom integracijom sistema<br />diferencijalnih jednačina modela primenom Runge-Kutta<br />metode IV reda.</p> / <p>The objective of this doctoral thesis was development of<br />mathematical model for complex three-phase reaction<br />system for soybean oil epoxidation with peracetic acid<br />formed in situ from acetic acid and hydrogen peroxide in a<br />presence of an ion exchange resin as catalyst. The local<br />concentrations of components in water and oil phases were<br />introduced into the model. In addition to reactions of the<br />peracetic acid and epoxy compound formation, model<br />considers the side reaction of epoxy ring cleavage with<br />acetic acid. Approximate modeling of peracetic acid<br />formation was based on Langmuir-Hinshelwood-Hougen-<br />Watson and Rideal-Eley postulates. Established threephase<br />model is a system of ordinary first order differential<br />equations which describes change of components and<br />functional groups amounts with reaction time. Besides<br />kinetic parameters, model comprises the thermodynamic<br />ones as well as parameters of mass transfer between the oil<br />and water phase. All model parameters are dependent on<br />temperature and some additionally on composition and<br />intensity of stirring.<br />A semitheoretical temperature dependency of chemical<br />equilibrium constant for peracetic acid formation was<br />established. The order of magnitude and temperature trend<br />of the calculated chemical equilibrium constant are in<br />agreement with the most data given in a literature.<br />For calculation of partition coefficient for acetic acid<br />between oil and water phase, temperature and composition<br />dependency of liquid-liquid equilibrium constant for acetic<br />acid is necessary. It was found that UNIFAC model of<br />group contribution was non-applicable for the prediction<br />of the equilibrium constant. The experimental data for the<br />equilibrium constant were, however, successfully fitted by<br />UNIQUAC model.<br />Temperature dependencies of the reaction rate constants<br />and sorption constants of reactants and products in<br />peracetic acid formation reaction are expressed by<br />reparameterized Arrhenius equation. The parameters of<br />such equation were determined simultaneously with mass<br />transfer parameters and ratio of peracetic acid and acetic<br />acid partition coefficients between oil and water phase by<br />fitting the experimental data i.e. by minimization of least<br />sum of squares of deviation between the calculated and<br />experimentally determined iodine value and epoxy oxygen<br />content . Marquardt method was successfully used to fit<br />the experimental data. A fourth-ordered Runge-Kutta<br />method was applied for integrating the system of<br />differential equations of the model.</p>

Acid/base and metal ion adsorption properties have been investigated for a range of chemically modified bleached Kraft fibre materials (pulps). The studies were performed via potentiometric titrations, Flame Atomic Absorbtion (and Emission) Spectroscopy, Inductively Coupled Plasma Optical Emission Spectroscopy and Extended X-ray Absorbtion Fine Structure measurements. As a result of a chemical modification procedure, the total concentration of acidic carboxylate groups in the fibre materials ranged between 43 and 590 μmol/g. The preferable surface potential model for modelling the ionic strength dependent acid/base properties of fibre materials with low charge densities, i.e. unmodified fully bleached Kraft fibre materials, was found to be the Basic Stern Model. For fibre materials with high total charge, ≳100 μmol/g, this model resulted in poor fits to data, and for such materials a number of Constant Capacitance Models, one at each ionic strength, must be recommended. With respect to metal ion adsorption, the results have indicated that the unspecific Donnan theory could correctly model the simultaneous adsorption of several metal ions, i.e. K+, Na+, Mg2+, Ca2+ and Cu2+, provided that the salt concentration in the fibre suspension is low. In suspensions of high salt concentration it was, however, found that this very same model strongly underestimated the adsorption of Ca2+ and Cu2+. Here, the Donnan model had to be complemented by specific ion exchange equilibria. These results were corroborated by spectroscopic evidence of specific interactions between Cu2+-ions and fibres. The spectroscopic indication of a complex formed between two fibre surface carboxylate groups and one Cu2+-ion, agree with the specific ion exchange model. It was therefore concluded that specific metal ionfibre interactions cannot be neglected, especially at high salt concentrations. The interactions occurring between the polycation GaO4Al12(OH)24(H2O)127+ and fibre materials were studied by both adsorption and spectroscopic measurements. These indicate that GaO4Al12(OH)24(H2O)127+ is surprisingly stable in fibre suspensions and that intact GaO4Al12(OH)24(H2O)127+- ions are strongly adsorbed onto the fibres. Also for this ion, specific interactions has to be considered, since the strong adsorption registered was too strong to be explained by Donnan equilibria. In the thesis, the stochiometric composition and an equilibrium constant characterising these interactions is presented.

Metallic fuels have an important role to play in "fast breeder" Gen-IV type nuclear reactors, and U-Pu-Zr is one of the prototypical systems. Because of the variability in fuel chemistry during burn-up, it is important to understand the effect of minor actinides and fission products on phase stability. Within this framework, we present a study on phase equilibria in the binary Np-Zr alloy system on which little work has been published. To resolve the contradictory reports on the ordering/ clustering trends of the bcc phase, a thermodynamic study is performed using the CALPHAD method. The calculated Np-Zr phase diagram is consistent with two sets of data: formation enthalpies of the bcc phase that are calculated with ab initio KKR-ASA-CPA electronic-structure method and lattice stabilities of solution phases obtained from first-principles technique. Another important feature in the Np-Zr alloy system is the non-stoichiometric delta-NpZr2 phase that forms in a hexagonal C32 structure similar to the delta-phase in the U-Zr system and the w-phase in pure Zr. An increase in the homogeneity range of the delta-phase when going from Pu to Np and to U is attributed to a lowering of its heat of formation that is caused by an increase in d-band occupation. Two different possibilities for the stability of the delta- and w- phases have been proposed in the present work. Additionally, calculated changes in enthalpy versus temperature are plotted for two alloy compositions of the Np-Zr system to guide future experimental work in resolving important issues in this system. Finally, an ab initio study, implemented with the L(S)DA U formalism, is performed for pure Np that reveals a transition from a non-magnetic to a magnetic state at a critical U parameter.

<p>The main focus in the present work concerns calculations on steel/slag equilibria. Thermodynamic software and databases are now powerful and accurate enough to give reliable results when applied to complex metallurgical processes. One example is the decarburization process of high alloyed steels. It is shown that using advanced thermodynamic models, without a complicated kinetic description of the system, reasonable agreement with experimental data is obtained. The calculations are performed using the Thermo-Calc software.</p><p>Within this work a Java interface for Thermo-Calc has been implemented. Java gives graphical possibilities and a graphical interface has been created that facilitates calculations that involve both metallic phases as well as oxides and make them feasible also for an industrial user.</p>

No description available.

In this PhD research the liquid-liquid phase separation phenomena in Gd-based alloys was investigated in terms of phase equilibria, microstructure formation upon quenching the melt and corresponding magnetic properties of phase-separated metallic glasses. The phase diagrams of the binary subsystems Gd-Zr and Gd-Ti were experimentally reassessed. Especially the phase equilibria with the liquid phase could be determined directly by combining in situ high energy synchrotron X-ray diffraction with electrostatic levitation of the melt. The Gd-Zr system is of eutectic type with a metastable miscibility gap. The eutectic composition at 18 ± 2 at.% Zr, the liquidus line and the coexistence of bcc-Zr and bcc-Gd at elevated temperature could be determined. The Gd-Ti system is a monotectic system. The experimental observations in this work led to improved new Gd-Zr and Gd-Ti phase diagrams. The phase equilibria of the ternary Gd-Ti-Co system were analyzed for two alloy compositions. The XRD patterns for molten Gd35Ti35Co30 gave direct evidence for the coexistence of two liquid phases formed by liquid-liquid phase separation. The first experimental and thermodynamic assessment of the ternary Gd–Ti–Co system revealed that the stable miscibility gap of binary Gd–Ti extends into the ternary Gd–Ti–Co system (up to about 30 at.% Co). New phase-separated metallic glasses were synthesized in Gd-TM-Co-Al (TM = Hf, Ti or Zr) alloys. The microstructure was characterized in terms of composition and cooling rate dependence of phase separation. Due to large positive enthalpy of mixing between Gd on the one side and Hf, Ti or Zr on the other side, the alloys undergo liquid-liquid phase separation during rapid quenching the melt. The parameters determining the microstructure development during phase separation are the thermodynamic properties of the liquid phase, kinetic parameters and quenching conditions. By controlling these parameters and conditions the microstructure can be tailored both at microscopic and macroscopic length scales. This includes either droplet-like or interconnected microstructures at the microscopic level and glass-glass or glass-crystalline composites at the macroscopic level. Essential parameter for the quenched in microstructure is the temperature dependence of liquid-liquid phase separation, which is determined by the chemical composition of the alloy: on the one hand, earlier and/or later stages of spinodal decomposition or almost homogeneous glassy states are obtained if the critical temperature of miscibility gap Tc is close to the glass transition temperature Tg; and on the one hand, coarsening and secondary precipitations of the liquids are obtained if Tc is much higher than Tg. Finally, the influence of the microstructure developed by phase separation on their magnetic properties had been investigated. The saturation magnetization σS depends on the overall amount of Gd atoms in the alloys and is not remarkably affected by phase separation processes. The Curie temperature TCurie of the magnetic transition is influenced by the changed chemical composition of the Gd-rich glassy phases compared to that of monolithic Gd-Co-Al glasses. / In dieser Doktorarbeit wurde die flüssig-flüssig Phasenentmischung von Gd-basierten Legierungen hinsichtlich der Phasengleichgewichte, der Gefügeentwicklung während der Schmelzabschreckung und dazugehöriger magnetischer Eigenschaften, untersucht. Die Zustandsdiagramme der binären Untersysteme Gd-Zr undGd-Ti wurden experimentell ermittelt.. Insbesondere konnten die Phasengleichgewichte mit der flüssigen Phase mittels in-situ Röntgenbeugungsmessunngen an elektrostatisch levitierten Schmelzen direkt, bestimmt werden. Das Gd-Zr System stellt ein ein eutektisches Phasendiagram dar und besitzt eine metastabile Mischungslücke. Die eutektische Zusammensetzung wurde mit 18 ± 2 at.%Zr bestimmt und der Verlauf der Liquiduslinie bei erhöhten Temperaturen wurde experimentell ermittelt. Experimentell wurde die Koexistenz von kubisch-raumzentrierten Zr und Gd in einem Bereich bei hohen Temperaturen nachgewiesen. Das Gd-Ti-System ist von monotektischer Art. Die experimentellen Beobachtungen dieser Arbeit trugen wesentlich zur Verbesserung der Beschreibung der Phasendiagaramme Gd-Zr- und Gd-Ti-Phasenbei. Die Phasengleichgewichte des ternären Gd-Ti-Co-Systems wurde anhand zweier Legierungszusammensetzungen untersucht. Die Röntgenbeugungsdiffraktogramme der geschmolzenen Legiereung Gd35Ti35Co30 sind ein direkter Beleg für die Koexistenz zweier flüssiger Phasen, aufgrund der flüssig-flüssig Phasenentmischung. Die erste experimentelle und thermodynamische Auswertung des ternären Gd-Ti-Co-Systems zeigt, dass sich die stabile Mischungslücke des binären Gd-Ti-Systems ins ternäre Gd-Ti-Co-System bis zu ungefähr 30 at.% Co erstreckt. Es wurden neue Gd-TM-Co-Al (TM = Hf, Ti oder Zr)-basierte metallische Gläser, die separierte Phasen besitzen, hergestellt. Ihr Gefüge wurden hinsichtlich Zusammensetzung- und Abkühlratenabhängigkeit der Phasenentmischung charakterisiert. Aufgrund der großen positiven Mischungsenthalpie zwischen Gd auf der einen und Hf, Ti oder Zr auf der anderen Seite, weisen diese Legierungen eine flüssig-flüssig Phasenentmischung während der Abschreckung aus der Schmelze auf. Die Einflussgrößen, die die Gefügeentwicklung während der Phasenentmischung bestimmen, sind die thermodynamischen Eigenschaften der flüssigen Phase, die kinetische Parameter und die Abschreckbedingungen. Indem diese Parameter und Bedingungen kontrolliert werden, kann das Gefüge auf makro- sowie mikroskopischer Längenskala maßgeschneidert werden. Dies beinhaltet entweder tropfenförmige oder miteinander verbundene Gefüge auf einer mikroskopischen Skala und Glas-Glas oder Glas-Kristall Komposite auf einer makroskopischen Längenskala. Ein wesentlicher Parameter für das abgeschreckte Gefüge ist die Temperatur-Abhängigkeit der flüssig-flüssig Phasenentmischung, die durch die chemische Zusammensetzung der Legierung bestimmt wird. Frühere und/oder spätere Stadien der spinodalen Entmischung oder nahezu homogene amorphe Zustände können abhängig von dem Temperaturunterschied zwischen kritischer Temperatur der flüssig-flüssig Phasenentmischung und der Glasübergangstemperatur erhalten werden. Wenn die kritische Temperatur der Mischungslücke, Tc, viel höher ist als die des Glasübergangs, Tg, können makroskopische Vergröberungen der tropfenförmigen Verteilung der flüssigen Phase und sekundäre flüssige oder kristalline Ausscheidungen in den gebildeten amorphen Phasen erhalten werden. Durch die Phasenentmischung und die erhaltenen heterogenen Gefüge werden die magnetischen Eigenschaften beeinflusst.. Die Sättigungsmagnetisierung,σS, hängt von der gesamten Anzahl der Gd-Atome der Legierung ab und wird nicht bemerkenswert vom Phasenentmischungsprozess beeinflusst. Die Curie Temperatur TCurie wird im Vergleich zu monolithischen Gd-Co-Al Gläsern, und abhängig von der chemischen Zusammensetzung der Gd-reichen Phase, verändert.