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Solid-Liquid Equilibrium in Multi Solute SystemsKurosawa, Izumi 18 May 2004 (has links)
Solid-liquid equilibrium in isomorphous amino acid systems has been investigated as a model for systems that form solid solutions. Solid- and liquid-phase compositions in L-valine + L-leucine, L-valine + L-isoleucine, and L-isoleucine + L-valine in water were measured over the entire range of solid composition, and it was shown (from mass balance and phase rule considerations) that these systems form solid solutions. The solid- phases resulting from isothermal and cooling crystallization experiments were also investigated using powder x-ray diffractometry which showed that homogeneous solid solutions could only be obtained in cooling crystallization experiments, whereas isothermal experiments generally produced inhomogeneous solids. This suggests that data reported in the literature from isothermal experiments may not represent true equilibrium values. Solid-phase activity coefficients were estimated using binary and ternary equilibrium data and the UNIFAC-Kuramochi model for liquid-phase nonidealities. The solid phases in the three systems investigated exhibited significant nonidealities that were correlated using the Margules model. The model parameters exhibited a linear relationship with the ratio of binary solubilities of the two solutes. Such simple relationship may be advantageous when solid-liquid equilibrium of thermally unstable solutes or components with unknown physical properties are crystallized.
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PSEUDO-TERNARY PHASE DIAGRAMS OF A DRUG DELIVERY SYSTEMWang, Ziheng 01 May 2009 (has links)
The purpose of this research was to develop the pseudo-ternary phase diagrams for a model drug delivery system consisting of vitamin E (model drug) + soybean oil + surfactant + co-surfactant (anhydrous glycerol) + water. The model drug (vitamin E) was loaded in the oil phase. The effects of different surfactants (pure and mixed) on the phase diagram, especially the microemulsion region, were investigated. The influence of drug loading level on the phase diagram was also determined. The surfactants studied were Tween 20, Tween 80, Cremopher EL, and their mixtures. The size (area) of the microemulsion region of the phase diagram was found to be dependent on the type of surfactant used and the loading level of drug (vitamin E).
The phenomenon of phase inversion from W/O microemulsion to O/W microemulsion was also investigated for the drug delivery system consisting of soybean oil (0% w/w Vitamin E loading or 30% w/w Vitamin E loading) + Tween 80 + anhydrous glycerol + water. The inversion of phases was detected by observing changes in the viscosity of the system.
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PSEUDO-TERNARY PHASE DIAGRAMS OF A DRUG DELIVERY SYSTEMWang, Ziheng 01 May 2009 (has links)
The purpose of this research was to develop the pseudo-ternary phase diagrams for a model drug delivery system consisting of vitamin E (model drug) + soybean oil + surfactant + co-surfactant (anhydrous glycerol) + water. The model drug (vitamin E) was loaded in the oil phase. The effects of different surfactants (pure and mixed) on the phase diagram, especially the microemulsion region, were investigated. The influence of drug loading level on the phase diagram was also determined. The surfactants studied were Tween 20, Tween 80, Cremopher EL, and their mixtures. The size (area) of the microemulsion region of the phase diagram was found to be dependent on the type of surfactant used and the loading level of drug (vitamin E).
The phenomenon of phase inversion from W/O microemulsion to O/W microemulsion was also investigated for the drug delivery system consisting of soybean oil (0% w/w Vitamin E loading or 30% w/w Vitamin E loading) + Tween 80 + anhydrous glycerol + water. The inversion of phases was detected by observing changes in the viscosity of the system.
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Fázový diagram chladiva LiF-NaF-KF / LiF-NaF-KF Coolant Phase DiagramMikula, Hynek January 2010 (has links)
In introduction this graduation theses discource about phase diagrams and thein fission. Next part is about concrete phase diagrams NaF – KF, NaF – LiF, KF – LiF. Their determination trough use of cooling surves and their specification trough use of numerical method. Conclusion contains proposal of method for concrete phase diagram of NaF – KF – LiF.
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Determination of the Fe-Cr-Ni and Fe-Cr-Mo Phase Diagramsat Intermediate Temperatures using a NovelDual-Anneal Diffusion-Multiple ApproachCao, Siwei January 2013 (has links)
No description available.
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Formation and physicochemical properties of crystalline and amorphous salts with different stoichiometries formed between ciprofloxacin and succinic acidPaluch, Krzysztof J., McCabe, T., Müller-Bunz, B., Corrigan, O.I., Healy, A.M., Tajber, L. 15 August 2013 (has links)
Yes / Multi-ionizable compounds, such as dicarboxylic
acids, offer the possibility of forming salts of drugs with
multiple stoichiometries. Attempts to crystallize ciprofloxacin,
a poorly water-soluble, amphoteric molecule with succinic acid
(S) resulted in isolation of ciprofloxacin hemisuccinate (1:1)
trihydrate (CHS-I) and ciprofloxacin succinate (2:1) tetrahydrate
(CS-I). Anhydrous ciprofloxacin hemisuccinate (CHS-II)
and anhydrous ciprofloxacin succinate (CS-II) were also
obtained. It was also possible to obtain stoichiometrically
equivalent amorphous salt forms, CHS-III and CS-III, by spray
drying and milling, respectively, of the drug and acid. Anhydrous CHS and CS had melting points at ∼215 and ∼228 °C, while
the glass transition temperatures of CHS-III and CS-III were ∼101 and ∼79 °C, respectively. Dynamic solubility studies revealed
the metastable nature of CS-I in aqueous media, resulting in a transformation of CS-I to a mix of CHS-I and ciprofloxacin 1:3.7
hydrate, consistent with the phase diagram. CS-III was observed to dissolve noncongruently leading to high and sustainable drug
solution concentrations in water at 25 and 37 °C, with the ciprofloxacin concentration of 58.8 ± 1.18 mg/mL after 1 h of the
experiment at 37 °C. This work shows that crystalline salts with multiple stoichiometries and amorphous salts have diverse
pharmaceutically relevant properties, including molecular, solid state, and solubility characteristics. / Solid State Pharmaceutical Cluster (SSPC), supported by Science Foundation Ireland under grant number 07/SRC/ B1158.
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Linker-based Lecithin Oral Drug Delivery SystemsChu, Jacquelene 04 December 2012 (has links)
In this study, pharmaceutical-grade and food-grade linker-based lecithin self-emulsifying delivery systems (SEDS) were developed with a combination of lipophilic and hydrophilic linkers. These additives at suggested concentrations are safe for pharmaceutical and food applications. The ratio of surfactant lecithin and linkers in these systems was optimized to develop surfactant in oil preconcentrates. The preconcentrates containing different surfactant concentrations and oil were diluted with fed state simulated intestinal fluid to produce pseudo-ternary phase diagrams and to identify the formulations that produced self-emulsifying or self-microemulsifying delivery systems. Optimal SEDS preconcentrates were evaluated using a dialyzer model to simulate intestinal uptake. An uptake of 39.6 mg/cm2 for the pharmaceutical-grade SEDS was obtained within 72 minutes, which promises substantial improvement in the bioavailability of hydrophobic actives. The optimal uptake of 12.2 mg/cm2 for food-grade SEDS suggests enhancement in the bioavailability of omega-3 fatty acids.
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Linker-based Lecithin Oral Drug Delivery SystemsChu, Jacquelene 04 December 2012 (has links)
In this study, pharmaceutical-grade and food-grade linker-based lecithin self-emulsifying delivery systems (SEDS) were developed with a combination of lipophilic and hydrophilic linkers. These additives at suggested concentrations are safe for pharmaceutical and food applications. The ratio of surfactant lecithin and linkers in these systems was optimized to develop surfactant in oil preconcentrates. The preconcentrates containing different surfactant concentrations and oil were diluted with fed state simulated intestinal fluid to produce pseudo-ternary phase diagrams and to identify the formulations that produced self-emulsifying or self-microemulsifying delivery systems. Optimal SEDS preconcentrates were evaluated using a dialyzer model to simulate intestinal uptake. An uptake of 39.6 mg/cm2 for the pharmaceutical-grade SEDS was obtained within 72 minutes, which promises substantial improvement in the bioavailability of hydrophobic actives. The optimal uptake of 12.2 mg/cm2 for food-grade SEDS suggests enhancement in the bioavailability of omega-3 fatty acids.
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Etude des diagrammes de phases ternaires La2O3 - Nb2O5 - (W/Mo)O3 et exploration des propriétés de conduction ionique / Study of ternary phase diagrams La2O3 - Nb2O5 - (W/Mo)O3 and investigation of ionic conduction propertiesVu, Tuong-Dan 05 October 2016 (has links)
La2Mo2O9, premier composé de la famille LAMOX, est intéressant pour des applications comme électrolyte dans des piles à combustible car il présente une conductivité ionique élevée. Il a été découvert durant l'investigation du diagramme de phases de La2O3 -MoO3. Cela montre bien le rôle important de l'étude de diagrammes de phase dans la découverte de nouveaux matériaux qui est devenue un objectif majeur de nombreux chimistes du solide. Selon ce concept, les deux diagrammes de phases ternaires La2O3-Nb2O5-WO3 et La2O3-Nb2O5-MoO3 ont été explorés et analysés pour la première fois en utilisant la synthèse par voie solide. Les structures des échantillons obtenus ont été caractérisées par diffraction des rayons X et des neutrons sur poudre et par microscopie électronique en transmission tandis que leurs propriétés électriques ont été testées par spectroscopie d'impédance complexe sur des pastilles frittées.La majorité des zones mono-, bi- et tri-phasées de ces deux diagrammes ont été définies. Plus particulièrement, les structures de deux nouvelles phases La3NbWO10 et La5NbMo2O16 ont été résolues ab-initio. La connaissance des structures des 2 nouveaux composés a permis une meilleure approche du diagramme de phase ternaire. D'une part, la mailleLa3NbWO10 est une sur structure de la maille fluorine(2aF*2aF*2aF) avec un axe c allongé. En considérant la formulation La18Nb6W62O604 (Z = 6), on constate aisément que la structure présente 2 types de défauts:des lacunes anioniques et cationiques sur les sites des atomes d'oxygène et de lanthane. D'autre part, la phaseLa5NbMo2O16 est un isotype du composé Pr5Mo3O16. Sa maille correspond aussi à une surstructure fluorine. Elle cristallise dans un système cubique (a = 11.22 Å) avec le groupe d'espace rare Pn n. Ce composé est prometteur puisqu'il présente une conductivité par les ions oxyde proche de celle de La2Mo2O9 à basse température. / La2Mo2O9, the first compound in the LAMOX family, is interesting for its applications as electrolytes in fuel cells because it presents a high ionic conductivity. It was discovered during the investigation of La2O3 - MoO3phase diagram. That shows the important role of phase diagram study in the discovery of new materials which has become a major objective of many solid chemists.In this concept, two ternary phase diagrams of La2O3-Nb2O5-WO3 and La2O3-Nb2O5-MoO3 were explored and analyzed for the first time using the solid-state synthesis. The structures of the obtained samples were characterized by the powder X-ray and neutron diffraction and by the transmission electronic microscopy. Besides, their electric properties were tested by the complex impedance spectroscopy onsintered pellets.As results, most of the mono-, bi-, tri-phase zones in the title phase diagrams have been defined. Particularly, during the phase-diagram investigation, the structures of two new phases La3NbWO10 and La5NbMo2O16 were ab-initio resolved. Firstly, the La3NbWO10 cell is asuperstructure of a fluorine (2aF*2aF*2aF) with the lengthened c axis. Considering the La18Nb6W62O604(Z = 6) formulation, we can easily note that the structure presents 2 types of defaults: cationic and anionic vacancies. Secondly, the La5NbMo2O16 phase is isotype of Pr5Mo3O16 compound. Its cell is also a fluorine superstruture. It crystallized in a cubic system (a = 11.22Å) with the space group Pn n. The compound is promising because it presents an oxygen conductivity comparable to that of La2Mo2O9 at low temperature.
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High-Resolution Studies of Silicide-films for Nano IC-ComponentsJarmar, Tobias January 2005 (has links)
<p>The function of titanium- and nickel-silicides is to lower the series resistance and contact resistivity in gate, source and drain contacts of an integrated circuit transistor. </p><p>With decreasing dimensions, the low resistivity C54 TiSi<sub>2</sub> is not formed and stays in its high resistivity phase C49. It was found that a layer of niobium interposed between titanium and silicon, which is supposed to promote the C54 phase, led to the formation of the high resistivity C40 (Ti,Nb)Si<sub>2</sub> in both small and large contacts. </p><p>Increased interest in Si<sub>1-x</sub>Ge<sub>x</sub> layers led to the inclusion of the Ni-Si-Ge system in this project. The interaction between nickel and poly-Si<sub>0.42</sub>Ge<sub>0.58</sub> was found to be different from nickel and poly-silicon in the meaning of the phases formed during high temperature annealing. High-resistivity NiSi<sub>2</sub> was formed at 750°C, but nickel and Si<sub>0.42</sub>Ge<sub>0.58</sub> formed no disilicide. A massive out-diffusion of germanium from the NiSi<sub>1-u</sub>Ge<sub>u</sub> resulted in agglomeration at lower temperatures than for NiSi. This was ascribed to the larger enthalpy of formation for nickel reacting with silicon than with germanium. Ternary phase diagrams, with and without the disilicide phase, were calculated. According to the tie lines, NiSi<sub>1-u</sub>Ge<sub>u</sub> will be in thermodynamic equilibrium with Si<sub>1-x</sub>Ge<sub>x</sub> when u is smaller than x. This was confirmed experimentally, where a balanced germanium concentration in NiSi<sub>1-u</sub>Ge<sub>u</sub> and Si<sub>1-x</sub>Ge<sub>x</sub>, stabilized the germanosilicide. When nickel interacted with strained and relaxed silicon-germanium it was established that a strained substrate led to a morphologically unstable NiSi<sub>1-u</sub>Ge<sub>u</sub>. The germanosilicide was highly textured on both (001) and (111) substrates. The texturing was explained by the absence of Ni(SiGe)<sub>2</sub> which forced NiSiGe to reorient so as not to resemble a digermanosilicide at the film/substrate interface. NiSi<sub>0.82</sub>Ge<sub>0.18</sub> formed on p<sup>+</sup>-Si<sub>0.82</sub>Ge<sub>0.18</sub> in CBKs grew laterally under the SiO<sub>2</sub>, defining the contact hole. The contact resistivity extracted by 3D modelling was 5×10<sup>-8</sup> Ωcm<sup>2</sup>.</p>
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